Section 2, South of Strabane to South of Omagh Ground

Section 2, South of Strabane to South of Omagh

Ground Investigation Report – Volume 1 Introduction and General Principles

August 2010 Document Ref No 718736-0600-R-007 Volume 1 of 10 For Department for Regional Development

Roads Service Ref GW163

Belfast Shorefield House 30 Kinnegar Drive Holywood County Down Northern Ireland BT18 9JQ

T 028 90424117 F 028 90427039 A5 WTC - Section 2 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

Document Control Sheet

Project Title A5 Western Transport Corridor

Report Title Section 2 - Ground Investigation Report - Volume 1 Introduction and General Principles

Report Reference 718736-0600-R-007 Vol 1 of 10

Version A

Issue Date August 2010

Record of Issue

Version Status Author & Date Checked & Date Authorised & Date

A For R O’Hagan 08/10 A Wheeler 02/09/10 D Towell comment C McDermott 08/10 P Brown 08/10 J Kelly 08/10

Distribution

Organisation Contact Format Copies

DRD Roads Service Western C Loughrey – Project Pdf 1 Division Sponsor

DRD Roads Service HQ W Kerr – Engineering Pdf 1 Policy Unit

Jacobs Engineering UK Limited Lee Davison Pdf 1 (on behalf of RS HQ)

Mouchel Derek Parody Project Pdf 1 Manager

Table 1-1 Geotechnical Reports – List of Volumes

GIR Report Number Title Start End Volume CH CH

1 718736-0600-R-007 Introduction and General 27000 57600 Vol 1 of 10 Principles

2 718736-0600-R-007 Findings of the Investigation, 27000 33000 Vol 2 of 10 Section 2A

3 718736-0600-R-007 Findings of the Investigation, 33000 41100 Vol 3 of 10 Section 2B

4 718736-0600-R-007 Findings of the Investigation, 41100 44500 Vol 4 of 10 Section 2C

5 718736-0600-R-007 Findings of the Investigation, 44500 48000 Vol 5 of 10 Section 2D

6 718736-0600-R-007 Findings of the Investigation, 48000 49800 Vol 6 of 10 Section 2E

7 718736-0600-R-007 Findings of the Investigation, 49800 51200 Vol 7 of 10 Section 2F

8 718736-0600-R-007 Findings of the Investigation, 51200 57600 Vol 8 of 10 Section 2G

9 718736-0600-R-007 Environmental Testing Vol 9 of 10 Analysis

10 718736-0600-R-007 Risk Register Vol 10 of 10

This Volume is the Volume highlighted in Bold

LIMITATIONS

This report is presented to the Roads Service in respect of A5 Western Transport Corridor (WTC) - Section 2 and may not be used or relied on by any other person or by the client in relation to any other matters not covered specifically by the scope of this Report.

Notwithstanding anything to the contrary contained in the report, Mouchel Limited is obliged to exercise reasonable skill, care and diligence in the performance of the services required by the Roads Service and Mouchel Limited shall not be liable except to the extent that it has failed to exercise reasonable skill, care and diligence, and this report shall be read and construed accordingly.

This report has been prepared by Mouchel Limited. No individual is personally liable in connection with the preparation of this report. By receiving this report and acting on it, the client or any other person accepts that no individual is personally liable whether in contract, tort, for breach of statutory duty or otherwise.

Mouchel has used reasonable skill, care and diligence in the design and interpretation of the ground investigation, however, the inherent variability of ground conditions allows only definition of the actual conditions at the location and depths of exploratory holes and samples/tests therefrom, while at intermediate locations conditions can only be inferred.

New information, changed practices or new legislation may necessitate revised interpretation of the report after the date of its submission

Contents

1 Executive Summary...... 10 2 Introduction...... 12 2.1 Description of the Project...... 12 2.2 Scope and Objective of the Report ...... 18 2.3 Geotechnical Category of Project ...... 20 2.4 Other Relevant Information...... 21 3 Existing Information...... 22 3.1 Sources of Information...... 22 3.2 Previous Ground Investigations ...... 25 4 Field and Laboratory Studies...... 26 4.1 Walkover Survey ...... 26 4.2 Geomorphological/Geological Mapping ...... 26 4.3 Ground Investigation ...... 26 4.4 Drainage Studies...... 31 4.5 Geophysical Survey...... 32 4.6 Pile Tests...... 32 4.7 Other Field Work ...... 32 4.8 Laboratory Investigation ...... 32 5 Ground Summary ...... 36 5.1 Geography...... 36 5.2 Topography ...... 37 5.3 Historical Development...... 37 5.4 Man-made Features – Mining and Quarrying...... 39 5.5 Hydrology ...... 39 5.6 Geology...... 40 5.7 Hydrogeology ...... 48 5.8 Geomorphology...... 50 6 Ground Conditions and Material Properties...... 51 6.1 Introduction...... 51 7 Geotechnical Risk...... 76 8 Basic Design Philosophy and Methodology...... 77 8.1 Introduction...... 77 8.2 Earthworks ...... 78 8.3 Highway Structures ...... 94 8.4 Strengthened Earthworks ...... 95 8.5 Drainage...... 95 8.6 Pavement Design, Subgrade and Capping...... 96 8.7 Contaminated Land ...... 98 8.8 Ground Treatment Including Treatment of any Underground Voids etc. ... 98 8.9 Specification Appendices...... 98 8.10 Instrumentation and Monitoring ...... 98 Principal Symbols ...... 99 References...... 102

Tables

Table 1-1 Geotechnical Reports – List of Volumes...... iv

Table 2-1: Section Limits...... 14

Table 2-2: Parties to the Project...... 17

Table 2-3: Report Volumes...... 18

Table 3-1: Sources of Information ...... 22

Table 3-2: Utilities ...... 25

Table 4-1: Drawings showing locations of field survey data ...... 26

Table 4-2: Summary of GI Works ...... 28

Table 4-3: Summary of Geotechnical Laboratory Testing...... 33

Table 5-1: Summary of Peat Extents ...... 41

Table 5-2 Summary of Precambrian Strata to the North of the OTF...... 45

Table 5-3: Carboniferous Stratigraphy ...... 46

Table 5-4 Strata to the south of the Omagh Thrust Fault...... 48

Table 6-1: Range of Field values of k h / k v ratio (after Bergado et al 1994) ...... 53

Table 6-2: Typical permeability values for Soils (Carter and Bentley, 1991).....54

Table 6-3: φφφ' for Siliceous Sands and Gravels...... 56

Table 6-4: Relationship between Cone Resistance, Phi and Young’s Modulus (Ref. Eurocode 7) ...... 58

Table 6-5: Critical Angle of Internal Friction from Plasticity Index (BS 8002)..62

Table 6-6: Overconsolidation Ratios (After Barnes, 2000) ...... 69

Table 6-7: Equilibrium Subgrade CBR Estimation...... 70

Table 6-8: Basic friction Angle on Discontinuities (after Barton and Choubey, 1977) ...... 72

Table 6-9: Modular Ratios (After Hobb’s 1974) ...... 75

Table 6-10: Rock Mass Factors (After Hobbs, 1974)...... 75

Table 8-1: Geomechanics Classification of Jointed Rock Mass (after Bieniawski, 1976) ...... 81

Table 8-2: Typical µ g Values (After Tomlinson, 2001)...... 86

Table 8-3: Diggability Index rating (after Trenter, 2001) ...... 94

Table 8-4: Excavation Diggability Classification (after Trenter, 2001)...... 94

Table 8-5: Principal Symbols ...... 99

Figures

Figure 2-1: Regional Context Plan...... 12

Figure 6-1: c h values derived from t 50 values (after Robertson et al 1992)...... 52

Figure 6-2: Relationship between N value, Phi and Relative Density (after Peck et al, 1967) ...... 55

Figure 6-3: Relationships between angles of internal friction and insitu tests 57

Figure 6-4: CPT N Value Correlation...... 59

Figure 6-5: Terzaghi and Peck method for Calculating Allowable Bearing Pressure ...... 60

Figure 6-6: Angle of Internal Friction Determined from Plasticity Index...... 61

Figure 6-7: Variation of f1 with Plasticity Index (after Tomlinson, 2001)...... 63

Figure 6-8: Variation of f2 with Plasticity Index (after Tomlinson, 2001)...... 65

Figure 6-9: Joint Roughness Co-efficient (After Barton & Choubey, 1977) ...... 73

Figure 8-1: Guidelines for the Design of Rock Traps (After Whiteside, 1986) ..82

Figure 8-2: Rock Slope Land Requirements ...... 83

Figure 8-3: Typical Section for Dig Out and Replace Sites...... 88

Figure 8-4: Excavability of Rock (after Petitifer and Fookes, 1994 and Harber et al, 2000)...... 92

Figure 8-5: Diggability Chart (after Trenter, 2001) ...... 93

Appendices

Appendix A – Geotechnical Certificate Appendix B – Guidance on Navigating the GIS Data

1 Executive Summary

The objective of the A5 Western Transport Corridor (A5 WTC) proposed scheme is to upgrade the A5 from New Buildings, south of Londonderry, to Aughnacloy to provide a high quality dual carriageway road to improve access to and stimulate regeneration of the northwest of the island of Ireland.

For logistical reasons the scheme has been split up in to three sections, New Buildings to South of Strabane (Section 1); South of Strabane to South of Omagh (Section 2) and South of Omagh to Aughnacloy (Section 3). This report provides the interpretation of a ground investigation carried out in Section 2 between September 2009 and March 2010. Section 1 and Section 3 of the scheme are reported separately.

Section 2 of the A5 WTC is approximately 30 km long. From a point to the east of Sion Mills in the north to the south of Newtownstewart, the proposed alignment trends northwest to southeast. South of Newtownstewart the alignment trends from north to south, through the Strule Valley and to the east of Omagh, before changing orientation to a northwest to southeast direction near the Section 2/Section 3 boundary, south of Omagh.

To the north of Newtownstewart the topography of the alignment is gently undulating on the western side of the River Mourne/Strule valley. To the south of Newtownstewart the alignment runs along the lower eastern slopes of Bessy Bell, a dominant hill to the west of the Strule. South of the Strule Valley the topography is dominated by drumlins. The route crosses the floodplain of the Fairy Water to the north of Omagh before entering another area of drumlins west and south of Omagh.

Superficial deposits in Section 2 are mostly tills, generally described as sandy gravelly clay. Glacial sand and gravel is also present, particularly in the north of the section. The till and the sand and gravel are interspersed with localised areas of peat and alluvium. The underlying solid geology of Section 2 is divided by the Omagh Thrust Fault, which crosses through the section in the south. To the north of the fault the geology is largely Precambrian in age and comprises metamorphosed sandstone and mudstone. There are also a number of Carboniferous outliers north of the fault comprising sandstone and siltstone. To the south of the fault Devonian sandstone is present underneath the superficial deposits.

The majority of the proposed scheme is agricultural greenfield land, however there are a number of active and former sand and gravel pits on or adjacent to the proposed alignment to the west and south of Newtownstewart and to the north of the River Derg. There are also a number of locations where there have been potentially contaminative former land uses. The most significant of these

being the former Great Northern railway line, which the alignment runs along for 1.5 km, to the north of the Fairy Water.

In June 2009, Mouchel designed and supervised a ground investigation of the proposed alignment. The fieldworks took place from September 2009 to March 2010 and comprised 252 No. cable percussion boreholes, 104 No. with rotary follow on, 202 No. trial pits, 91 No. window samples and 133 No. probes. The purpose of the investigation was to gain an understanding of the ground conditions along the proposed ssheme, to delineate the soft ground and to provide geotechnical parameters for design of the road pavement and the associated side slopes and structures.

Due to the size of Section 2 the Ground Investigation Report (GIR) for Section 2 is split into 10 sub volumes, this being Volume 1. This volume describes the purpose of the scheme, the general background of the investigation, a summary of the ground investigation and the conditions encountered plus a summary of the design principles. Volumes 2 to 8 of the GIR, describes in detail the ground conditions and the material properties of the 7 sub-sections of Section 2. These have been divided on the basis of topography, proposed works and geology. Volume 9 describes the results of the contamination testing carried out on soil samples taken in the Section and Volume 10 contains the geotechnical risk register for Section 2.

2 Introduction

2.1 Description of the Project

2.1.1 Regional Context

The A5 Western Transport Corridor is the main north-south route in the west of the province, connecting Dublin to Londonderry and Donegal. It links to three cross border routes: at Aughnacloy (N2), Strabane-Lifford (N14) and Londonderry (N13). On a Northern Ireland regional context, the A5 connects to the A4/M1 east-west route in the south of the province and the A6 Belfast – Londonderry route in the north of the province. The regional context is shown below in Figure 2-1.

Figure 2-1: Regional Context Plan

The scheme involves the upgrade of the A5, from the Irish border at Moy Bridge near Aughnacloy (H 127 412), via Omagh and Strabane to the southern outskirts of Londonderry in the vicinity of New Buildings (H 522 667), to dual carriageway standard with grade separated junctions.

2.1.2 Scheme Objectives

The objective of the proposed scheme is to upgrade the A5 from Aughnacloy to New Buildings, south of Londonderry, to provide a high quality dual carriageway road to improve access to and stimulate regeneration of the northwest of the island of Ireland.

The Roads Service objectives are to deliver the preferred route in accordance with the current standards in the DMRB and in accordance with the best current practice. Notwithstanding this, it is recognised that the volume of information to be handled will be substantial and innovative methods for handling / presenting data and managing stakeholders will be required which may go beyond the scope of current standards. A strong partnering ethos has been developed between all interested parties to optimise the delivery of the project.

2.1.3 Geotechnical Objectives

The geotechnical objectives in relation to the scheme are to identify and quantify any geotechnical and geo-environmental issues and risks arising from the ground, which may influence the design of the works and the associated land to be vested by the Department. Factors to be considered include the design, construction method, safety, cost and programme of construction and the geo-environmental impacts of the scheme. This will include (but is not limited to):

• Problematic former land uses including areas of contaminated land, old buildings, quarries, backfilled pits and mining

• The nature, distribution and thickness of glacial, alluvial and peat soils

• The nature, distribution and thickness of rock strata

• Hydrogeological conditions

• Topography and geomorphology

• Areas of potentially unstable soils such as peat bogs and rock slides

• Watercourse crossings

2.1.4 Scheme Section

For logistical reasons, the scheme has been divided into 3 sections:

Table 2-1: Section Limits Section Section Limits

1 New Buildings to South of Strabane

2 South of Strabane to South of Omagh

3 South of Omagh to Aughnacloy

Each section has been designed and reported on separately. This report relates only to Section 2.

2.1.5 Development of the Scheme

Mouchel were appointed in February 2008 to undertake engineering & environmental studies and designs to develop a specimen design that will be subject to a public inquiry in 2011.

The scheme evolved in three stages as follows:-

Stage 1 – evaluation of a study area up to 20km wide to identify a 1km wide preferred corridor, reported in the Preliminary Options Report (POR1)

Stage 2 – evaluation of alternative routes within the preferred corridor to identify a preferred route, reported in the Preferred Option Report (POR2). Geotechnical Factors affecting the selection of the preferred route were reported in the Preliminary Sources Study in May 2009. The Preferred Route was announced by the Minister for Regional Development in July 2009.

Stage 3 – development of a specimen design for the preferred route. This will be used to develop draft orders for the route that will be the subject of the public inquiry. A ground investigation was carried out between September 2009 and March 2010 to provide geotechnical data to inform the development of the specimen design and draft vesting orders. This document presents the findings of that ground investigation for Section 2 of the scheme.

2.1.6 Description of the Preferred Route in Section 2

The route is described below from north to south extending from approximately 200 m north of Primrose Park Road in the North of Sion Mills (CH 27000) to Seskinore Road, South of Omagh (CH 57600). The preferred route is located to the west of the existing A5 throughout Section 2.

• From north to south the route passes under Primrose Park Road at CH 27200 and continues through cutting under Bells Park Road at CH 28000. The route carries on through cutting until it passes under Seein Road at CH 29200 m.

• The route is then on embankment over a peat bog at CH 30500 and over Concess Road at CH 30150 and returning to cutting at CH 31000 for approximately 200 m.

• The route continues southeast at grade for approximately 200 m and then on embankment, crossing over Fyfin Road at CH 31500 to CH 31600. The route is in a small length of cutting to CH 32300, passing beneath Stone Road at CH 31900. To the south the route runs at grade and in sidelong ground until CH 33100.

• It then runs through cutting adjacent to three working quarries; two sand and gravel quarries to the east and a rock quarry to the west. The route passes beneath the Derg Road at CH 34000, crosses the Derg River at CH 34400 and passes under Deerpark Road at CH 34700.

• The route runs south at grade until approximately CH 36000 where it bends to the southwest on embankment, travels over Magheracoltan Road at CH 36300 and through Barons Court Road Junction at CH 37200. It is then on embankment and at grade to CH 38350.

• Continuing southeast the route passes through cutting adjacent to Harry Avery’s Castle, beneath Old Castle Road at CH 38600 and under Gortgranaghy Road at CH 39400. It then passes under Castletown Road for the first time at CH 39900 and a transition from cutting to embankment is present at CH 40600.

• The route runs on embankment passing over West Road at CH 41150 before gradually bending back to a southerly alignment as it enters the Strule Valley. Joes Lane passes over the route at CH 42500 and travels on sidelong ground, adjacent to the existing A5 until CH 44500, where the route runs through cutting to CH 45500, passing under Killinure Road at CH 44900.

• Running south westerly the route crosses Castletown Road for a second time at a location of soft/peaty ground at CH 53700. It then continues south through a mixture of short lengths of cutting, embankment, at grade and side long ground sections and through an area of soft ground (depth to 9 m below ground level (m bGL)) from CH 46400 to CH 46500. The

route runs through cutting to CH 47250 passing under Dunteige Road at CH 46950.

• From CH 47250 to Rash Road overbridge, at CH 48050, the route runs predominantly on embankment. A peat bog is present immediately to the east of the route between CH 48100 and CH 48450 and the route follows the line of a disused railway from CH 48100 to CH 48950.

• The route is in cutting until it meets the Omagh North Junction at CH 49200. It continues south, adjacent to the disused railway line and crosses the Fairy Water at CH 50000. The route then runs over the Fairy Water flood plain and an area of soft ground, which is to be crossed via a viaduct.

• The route crosses over an area of peat at CH 50750, and then under Gillygooly Road at CH 51250. For approximately 600 m the route travels over peaty ground with depths of peat recorded to 2 m bGL.

• The route passes under Aghnamoyle Road at CH 52000 before crossing an area of peat (depth to 3 m bGL) located between CH 52300 and 53200, passing over Tamlaght Road at CH 53200 and beneath Brookmount Road at CH 53750.

• Continuing south the route crosses Clanabogan Road Junction at CH 54000 and passes under Loughmuck Road at CH 54350. Between these two structures the route crosses the Omagh Thrust Fault.

• The route continues southeast, predominantly on embankment, until it passes under Beagh Road at CH 55900 where it runs through lengths of cutting, at grade and side long ground.

• The route proceeds beneath Ballynahatty Road at CH 56400 before bridging the Drumragh River at CH 56600. Maintaining a south-easterly direction the route undergoes a transition from embankment to cutting at CH 56700.

• Turning to the east the route crosses an area of peat from CH 56900 to CH 57000 and passes under Blackfort Road at CH 57000. Section 2 ends at CH 57600.

2.1.7 Parties to the Project

Table 2-2: Parties to the Project Employer & Overseeing Designer Organisation

Organisation DRD Roads Service Western Mouchel Limited Division

Address County Hall, Drumragh Avenue, Shorefield House, 30 Kinnegar Omagh,Co Tyrone, Northern Drive, Holywood, County Down Ireland, BT79 7AF Northern Ireland, BT18 9JQ

Telephone Tel (028) 8225 4111 Tel (028) 9042 4117

Contact Mr Conor Loughrey: Project Mr Andy Heap, Deputy Project Sponsor Manager

[email protected] [email protected]

Technical Approval Authority Designer’s Geotechnical Advisor

Organisation DRD Roads Service, Mouchel Limited Headquarters

Address Clarence Court, 10-18 Adelaide Shorefield House, 30 Kinnegar St, Belfast, BT2 8GB Drive, Holywood, County Down

Northern Ireland, BT18 9JQ

Telephone (028) 9054 0413 Tel (028) 9042 4117

Contact Mr Willie Kerr Mr David Towell

[email protected] [email protected]

GI Contractor Main Contractor

Organisation Soil Mechanics Sisk Roadbridge PTMcWilliams M1 Tougher Business Park Address Askern Road, Carcroft, Naas Doncaster, DN6 8DG Co Kildare Telephone 01302 723456 +353 (0)45 440 000

Contact Mr James Huntington Mr Liam Preston

[email protected] [email protected]

2.1.8 Contracts

The ground investigation was carried out in accordance with the specification in the Manual of Contract Documents for Highway Works, Volume 5, using the NEC3 Short Form of Contract.

During the development of the specimen design, main contractors for the construction of the scheme were appointed under an Early Contractor Involvement (ECI) framework, in order to obtain their experience and views on most practical and most economic construction methods.

This report is intended to present the ground model for the scheme and its associated risks, in accordance with the guidelines issued by the Highways Agency in HD22/08 “Managing Geotechnical Risk” and as adopted by the Roads Service.

2.2 Scope and Objective of the Report

As discussed in section 2.1.4, a separate Ground Investigation Report will be submitted for each section of the scheme. This document refers to Section 2, from South of Strabane to South of Omagh.

Because of the size of each section of the scheme, the Ground Investigation Report has been split into volumes as follows:-

Table 2-3: Report Volumes Volume Title

1 Introduction & General Principles

2 Findings of the investigation, Section 2A

CH 27000 m to 33000 m

3 Findings of the investigation, Section 2B

CH 33000 m to 41100 m

4 Findings of the investigation, Section 2C

CH 41100 m to 44500 m

5 Findings of the investigation, Section 2D

CH 44500 m to 48000 m

Volume Title

6 Findings of the investigation, Section 2E

CH 48000 m to 49800 m

7 Findings of the investigation, Section 2F

CH 49800 m to 51200 m

8 Findings of the investigation, Section 2G

CH 51200 m to 57600 m

9 Contaminated Land

10 Risk Register

Each volume of the report has generally been structured in accordance with the Ground Investigation Report Template in HD22/08. Although not strictly part of the Ground Investigation Report template, a Chapter 8 is used to detail the preliminary geotechnical design work carried out for the development of the specimen design and draft vesting line.

This volume, Volume 1, includes Chapters

1 – Executive Summary,

2 - Introduction,

3 – Existing Information and

4 – Field and Laboratory Studies for the section.

And introductions into Chapters

5 – Ground Summary (brief overview for the whole section)

6 – Ground Conditions and Material Properties (describes the published information and correlations used to supplement site and laboratory data to establish soil and rock parameters for the project)

8 – Basic Design Philosophy and Methodology (discusses a number of common design philosophies and concepts which have been developed for use across the scheme in order to provide best value)

Volumes 2 to 8 will include detailed chapters 5 and 6 on the Ground Summary and the Ground Conditions and Material Properties in accordance with the Ground Investigation Report Template in HD22/08. Risks particular to the sub- section are detailed in Chapter 7 and this feeds in to the risk register for the whole section.

Volumes 2 to 8 conclude with outline design recommendations for earthworks and foundations in the sub-section. These recommendations should be developed as part of the detailed design that will take place when the scheme has passed the public inquiry.

Because of the size of the scheme section at approximately 30km length, drawings are provided not on paper but as navigable layers on a GIS model. Appendix A contains a guide to navigating the model.

2.3 Geotechnical Category of Project

In accordance with the Principles of HD22/08 (implemented in Northern Ireland by Roads Service standard RSPPG_E_008), the geotechnical category of the project has been reviewed. It is considered that the general extent of the project would classify as Category 2 with particular elements classifying as Category 3.

• Category 2 - Projects which include conventional types of geotechnical structures, earthworks or activities, with no exceptional geotechnical risks, unusual or difficult ground conditions or loading conditions.

• Category 3 - Projects which involve geotechnical activities or structures which fall outside the limits of Categories 1 and 2. These projects include very large, unusual or complex geotechnical activities, structures and or those involving abnormal geotechnical risks or unusual or exceptionally difficult ground conditions.

For Section 2 the following geotechnical issues are currently considered as Category 3. However it should be noted that the Geotechnical Classification should be reviewed as the scheme progresses and additional geotechnical issues could be added to this Category 3 list.

• Piled embankment north of Dunteige Road

• Piled embankment south of Loughmuck Road

2.4 Other Relevant Information

Not used

3 Existing Information

A geotechnical Preliminary Sources Study Report (PSSR) for Section 2 was carried out by Mouchel in June 2009 (ref: 796036/0600/R/006A). The study reviewed the available published geological and geotechnical information for the proposed scheme.

This chapter provides a summary of the information that was collated and compiled during the preparation of the Section 2 PSSR and includes any new information received since the publication of the PSSR.

3.1 Sources of Information

The information records pertaining to the scheme that have been consulted and reviewed are summarised in Table 3-1: . The table also includes details of how the information is pertinent to the scheme.

Table 3-1: Sources of Information Information Source Data gathered Application of information Ordnance Survey Current OS mapping Man-made obstructions/voids/sources of contamination Historical Ordnance Survey of Man-made obstructions/voids/sources Northern Ireland Maps of contamination Historical mapping Digital historical mapping for 1830’s, 1860’s & 1900’s Former/present mining/quarrying and land-filling - Identification of geo- hazards Ortho Aerial photography Former/present mining/quarrying and (2006) land-filling - Identification of geo- hazards Aerial photographs (usually Former/present mining/quarrying and dating back to 1946) held by land-filling – Identification of geo- the Public Records Office hazards Soil Maps Determine soil types & other properties, geomorphology & physical geography, vegetation & land use Topography Maps Representation of the relief with contours Digital Terrain Mapping Digital representation of the relief

Information Source Data gathered Application of information Geological Survey of 1:250 000 Geological Map of Solid geology along route corridor Northern Ireland Northern Ireland (Solid Edition) (GSNI) 1:250 000 Geological Map of Quaternary deposits along route Northern Ireland (Quaternary corridor Edition) 1:250 000 Groundwater Identification of the vulnerability of Vulnerability Map of Northern groundwater to contamination - Aquifer Ireland recognition & groundwater conditions 1:250 000 Hydrogeological Hydrogeological risk assessment – Map of Northern Ireland Aquifer recognition & groundwater conditions 1:50 000 Solid Edition – Underlying Geology - Solid geology Sheets 11, 33, 34, 45, 46 along route corridor 1:50 000 Drift Edition – Underlying Geology - Drift deposits Sheets 11, 33, 34, 45, 46 along route corridor 6” Scale Field Maps Detailed Geological map Geological field slips Identification of likely ground conditions Mineral Extraction Records Former/present mining/quarrying and land-filling - Identification of mineral extraction hazards Borehole Records Historical information on geotechnical & groundwater conditions Abandoned Mines Records Former mining location of shafts adits & abandonment plans - Identification of mining hazards Oil/Gas Extraction Former or present oil/gas extraction Website - Mineral Licensing Minerals & petroleum exploration & development in Northern Ireland Website - Petroleum Petroleum Licensing: September 2004, Licensing map indicating licenses applied for by exploration companies Northern Ireland Contaminated Land Database Present/previous landfills & potentially Environment Agency contaminated sites (NIEA) Water Quality Management Sensitivity of ground/surface water for Unit drainage design, pollution incidents, consented industrial discharges, sewage discharges, designated groundwater extraction points. Industrial Pollution Unit Identification of industrial operations, COMAH sites – Enforcements, prohibitions, prosecutions Water Quality Includes GQA chemical & biological classification results for rivers Landscape Character Areas Landscape. Geological and biodiversity summaries Waste Licensing Unit Register of licensed & exempt sites

Information Source Data gathered Application of information Londonderry, Building Control Strabane, Omagh and Dungannon Environmental Health Records of potential contaminating District Councils sites/landfills/fuel installations Planning Department Planning Applications, geotechnical & contaminated land conditions The Department of Historical Ground Historical information on geotechnical Finance and Investigation Reports and groundwater conditions Personnel, Central Procurement Directive Geological Survey of Co. Monaghan Drift maps Drift geology for Northern / Republic of Ireland Ireland border area Quarry and mineral database Identification of mineral extraction sites and hazards for Northern Ireland / Republic of Ireland border area Land Slides in Ireland Location of historical land-slip areas Mouchel Internal A4/A5 Ballygawley PSSR & GI Records Records Intersection A5 Newtownstewart Bypass Geotechnical design details A5 WTC Preliminary Options Report

A5 WTC Geotechnical Walkover Survey Methodology A5 WTC Geotechnical Initial Key Constraints 796036-0600-R-003A A5 WTC Geotechnical Statement of Intent 796036-0600-R-00001 Public Records Current & Historical Ordnance Man-made obstructions/voids/sources Office Survey of Northern Ireland of contamination Maps Aerial photographs (usually Former/present mining/quarrying and dating back to 1946) held by land-filling the Public Records Office Department of Planning Service May provide reference to data Environment submitted with planning applications & (Planning Services) also mineral planning details British Geological GeoIndex Various Information including, SI’s, Survey Shafts & Adits, Mineral occurrence, topography, geology Department for Section Engineers: Information on ground conditions; Regional Subsidence; Earthwork Records; Development: Londonderry Previous Investigations Roads Service - Strabane Section Engineers Omagh Dungannon Agriculture & Rural Rivers Agency Culverted watercourses, low flow water Development: course and any pollution incidents to Rivers Agency watercourses

Information Source Data gathered Application of information Department of Website - Mosaic 4 Utilities Information on utilities from DRD Water Culture Arts & Service, Rivers Agency, DRD Roads Leisure Service, NTL, Phoenix Gas, & NIE.

A list of the Statutory Undertakers who have services present within Section 2 is provided in Table 3-2.

Table 3-2: Utilities

Authority Relevance to scheme Northern Ireland Electricity Predominantly overhead lines, some underground cables

British Telecom Overhead and underground copper cables Underground fibre optic Bytel Connections Underground fibre optic Virgin Media Underground fibre optic Eircom UK Underground fibre optic NI Water Predominantly water mains, some foul sewers

3.2 Previous Ground Investigations

The records from a number of previous site investigations undertaken by the Central Procurement Directorate (CPD) and Geological Survey of Northern Ireland (GSNI) were obtained and included within the PSSR. Mouchel also hold records for a number of historical ground investigations. All historical ground investigation locations are shown on Drawing No. 796036-0600-D-00062B and the exploratory hole logs can be viewed via hyperlinks on the GIS model. The majority of this information does not lie along the proposed route and is limited to Sion Mills, Victoria Bridge, Newtownstewart, and between Mountjoy and the south of Omagh. One historical investigation is located on line of the proposed route, to the south of Mountjoy.

The Preliminary Ground Investigation for the A5 scheme was completed in March 2009 and is described in detail in the PSSR. The exploratory hole logs are hyperlinked within the GIS model and are also shown on Drawing No. 796036-0600-D-062B.

The findings of the information sources listed in this Chapter, including a summary of the ground conditions are discussed in Chapter 5.

4 Field and Laboratory Studies

4.1 Walkover Survey

During preparation of the PSSR a drive through survey was undertaken on 3 rd and 4 th March 2008 to gain an initial familiarisation of the engineering study area. This was then supplemented by a more detailed walk over survey undertaken from 18 th March to 25 th April 2008. The survey was carried out from the public highway by suitably qualified Mouchel personnel and a Walkover Survey Report was produced (ref: 796036-0600-R-013). Extracts from the Walkover Report are available to view via hyperlinks within the GIS Model. A number of more detailed surveys of specific areas of interest such as quarries, landfill sites and areas of peat have been undertaken by Mouchel.

The key findings, observations and photographs from the surveys are shown on the Drawings detailed in Table 4-1.

Table 4-1: Drawings showing locations of field survey data Survey Drawing Ref. Drive through Survey Notes and Photographs 796036-0600-D-00063B Walkover Survey Reports and Photographs 796036-0600-D-00064B Mineral Extraction Sites and Landfill Survey 796036-0600-D-00065B Peat Survey 796036-0600-D-00066B

4.2 Geomorphological/Geological Mapping

No Geomorphological/Geological mapping was undertaken.

4.3 Ground Investigation

4.3.1 Description of Fieldwork

Rationale for Fieldwork

A preliminary ground investigation (GI) was undertaken in February and March 2009 within the preferred corridor to obtain outline geotechnical data to aid the selection of the preferred route. The exploratory hole locations for the preliminary GI are shown on Drawing No. 796036-0600-D-00062B. The

preferred route was then investigated by the main ground investigation with field works taking place between September 2009 and March 2010.

The purpose of the main ground investigation was to build on the findings of the PSSR and attain sufficient information relating to the ground and groundwater conditions along and around the proposed route alignment in order to obtain:

• a detailed knowledge of the stratigraphy of the route;

• reliable derivation of material parameters.

• assessment of the re-use potential of the materials encountered;

• assessment of safe angles of slope for embankments and cuttings in drift and rock;

• assessment of pavement foundation conditions;

• provide information for determining the type of foundations for structures

• Confirm the presence or otherwise of any elevated chemical concentrations on the site.

General Fieldwork Details

The preliminary ground investigation was undertaken by Soil Mechanics (SM), a subsidiary of Environmental Services Group Limited (ESGL). This investigation comprised windowless sampling and dynamic probing, undertaken by Paul Mullin Site Investigations, and Cone Penetration Testing subcontracted to Lankelma.

The main ground investigation was undertaken from September 2009 to March 2010 by Soil Mechanics. Lankelma undertook Cone Penetration Testing under sub-contract to Soil Mechanics.

The works were designed, specified and monitored full time by Mouchel.

The main ground investigation was undertaken in three phases:

Phase 1 – An initial first pass through the entire section to attain an overview of ground conditions. The Phase 1 GI was limited to boreholes (BH) formed by

cable percussive (CP) drilling and the installation of groundwater monitoring equipment in selected BHs, trial pitting and cone penetration testing (CPT).

Phase 2 – A more detailed investigation of the entire section. The Phase 2 GI comprised BHs formed by CP drilling and the installation of groundwater monitoring equipment at selected BHs, rotary follow on, trial pitting, windowless sampling and dynamic and Macintosh probing. Televiewer surveys were undertaken in selected boreholes at the locations of proposed rock cuttings.

Phase 3 – Further investigation to infill any gaps in the investigation and focus on structure sites. Specific areas were also targeted where marginal ground conditions were encountered in the previous phases. The Phase 3 GI consisted of BHs formed by CP drilling and the installation of groundwater monitoring equipment at selected BHs, rotary follow on, trial pitting, windowless sampling and dynamic and Macintosh probing. Televiewer surveys were undertaken in selected boreholes at the locations of proposed rock cuttings.

The total figures for the preliminary GI and each phase of the main GI are summarised in Table 4-2:

Table 4-2: Summary of GI Works Phase Type of Exploratory Hole No. of Holes Completed Preliminary GI CPT 2 Windowless sample 26 Dynamic Probe 39 Phase 1 BH 55 Rotary Follow on 3 Trial Pit 102 CPT 34 Phase 2 BH 54 Rotary Follow on 32 Trial Pit 87 Windowless sample with 75 Dynamic Probe Dynamic Probe 14 Macintosh Probe 5

Phase Type of Exploratory Hole No. of Holes Completed Phase 3 BH 143 Rotary Follow on 69 Trial Pit 13 Windowless sample with 16 Dynamic Probe Dynamic Probe 8 Macintosh Probe 15

The locations of all exploratory holes are shown on Drawing No. 796036-0600- D-00095A.

Due to the continual evolvement of the scheme, exploratory hole locations were relocated, removed and added during the fieldwork stage of the ground investigation and hence the numbering system was not sequential along the route.

Particular details of the investigation carried out at each structure and earthwork location are recorded on the structure/earthwork summary sheets included in the Appendices in Volumes 2 to 8.

An additional phase of GI is currently being planned to infill areas not previously investigated due to road alignment changes, re-location of structures and to gain additional information at areas of soft and organic material. The records and results from this phase of GI were not available at the time of writing but will be incorporated in later revisions of this report.

4.3.2 Soil Sampling

Extraction of undisturbed 100 mm diameter samples in boreholes was attempted at 1 m intervals up to 10 m depth and 1.5 m intervals thereafter in cohesive material. The number of undisturbed samples recovered was limited due to the granular content of the soils and therefore UT100 sampling was not attempted. Where sample recovery was poor Standard Penetration Tests (SPTs) were carried out directly after the undisturbed sample was attempted.

Representative bulk samples were taken from boreholes at 1 m intervals, from trial pits at 1 m intervals and at any change of strata, and from all inspection pits.

Small disturbed (tub) samples were taken at the same location as each bulk sample and from material recovered from Standard Penetration Tests.

Windowless samples were recovered in liners and later split for logging purposes. Where the liner was damaged/split in the drilling process the sample was transferred to a bulk bag.

Rock cores were extracted from boreholes scheduled for rotary follow on. Where possible, the barrel was fitted with a liner before drilling commenced. Where this was not possible due to heavily fractured rock ripping the liner and jamming in the barrel the core was placed in the liner post drilling to aid protection and preservation of the sample.

Environmental samples were taken from trial pits at specified locations where contamination was suspected. In addition, samples were also taken at random locations to prove Greenfield soils would not be chemically unsuitable for reuse and at intervals in areas of cut for waste acceptance criteria assessment. The environmental sampling comprised 1 No. 1 kg tub sample and 1 No. 250 g sample in an amber glass jar to preserve any volatile organic chemicals.

4.3.3 Borehole Installations

During the preliminary GI standpipes were installed in 13 No. windowless sample holes to a maximum depth of 4.6 m.

During the main GI groundwater monitoring instrumentation was installed in 135 boreholes in the form of 130 No. 19 mm piezometers and 5 No. standpipes. Groundwater monitoring instrumentation was installed at approximately 300 m centres along the proposed route alignment, more frequently at proposed earthwork locations and at either end of proposed culverts. A minimum of 1 installation at minor structures or likely locations of retaining walls, and a minimum of 2 at the location of major structures and retaining walls were installed.

The details and findings from the groundwater monitoring are discussed further in the relevant sub-section volumes of this Report.

4.3.4 Ground Investigation Factual Report

A copy of the factual report, undertaken by Soil Mechanics, for the main GI (Ref. A9101), is presented separately. The preliminary GI report (Ref. Y9901) was provided as Appendix C in the PSSR.

4.3.5 Results of In-Situ Tests

Standard Penetration Tests (SPT) were carried out in boreholes in accordance with BS EN ISO 22476-3, in order to assess the relative density of the granular soils. SPTs were also undertaken where undisturbed samples could not be recovered in cohesive material. The ‘N’ values (number of blows for 300 mm penetration), or blow count/penetration where full penetration was not achieved were recorded and are reported on the borehole logs. Calibration certificates for the SPT’s are provided in the Soil Mechanics factual report.

Cone Penetration Testing was undertaken in accordance with BS 1377-Part 9 at locations of suspected soft ground.

Due to the granular fraction of material present in the superficial deposits only a limited number of hand shear vanes were undertaken in the trial pits. The results are presented on the trial pit logs.

Falling head permeability tests were undertaken in select boreholes in accordance with BS5930.

Dynamic Probing was undertaken in accordance with BS EN ISO 22476-2 at locations of suspected soft ground and adjacent to Windowless Sample holes.

Hand held Macintosh Probing was undertaken by Mouchel at areas inaccessible by other means of exploration.

The results of the in situ testing, with the exception of the Macintosh Probing, are reported on the appropriate logs and included in the Soil Mechanics Factual Report (Ref: A9101). The interpretation of the in situ testing is presented graphically and discussed in more detail within the relevant sub-section Volumes of this report.

4.4 Drainage Studies

Extensive drainage studies and surveys have been carried out as part of the drainage modelling and preliminary drainage design for the scheme. These studies and surveys are covered elsewhere and are outside the scope of this report.

4.5 Geophysical Survey

Not Used

4.6 Pile Tests

Not Used

4.7 Other Field Work

Reference to the Environmental Statement (ES) (718736-3000-R-008) should be made for detailed analysis of the findings of environmental assessments, including the results of a well survey.

4.8 Laboratory Investigation

4.8.1 Description of Tests

After completion of each hole exploratory hole specific laboratory schedules were prepared by Mouchel for determination of geotechnical properties, for the assessment of potentially contaminated materials and for waste acceptance assessments. A summary of all testing undertaken is given in Table 4-3.

Classification tests undertaken included; moisture content, Atterberg limits, particle size distribution, bulk density and particle density.

Compaction tests undertaken included; determination of dry density/moisture content relationship (2.5 + 4.5 kg), moisture condition value (single point and moisture content relationship) and re-compacted California Bearing Ratio (CBR) (1 and 5 point) tests.

Strength and consolidation tests undertaken included; unconsolidated undrained triaxials (undisturbed and remoulded), consolidated undrained triaxial, shearbox and one dimensional oedometer tests.

Point Load Index, unconfined compressive strength and Los Angeles abrasion value tests were undertaken on rock cores.

Chemical tests undertaken included; pH, water soluble sulphate and organic matter content.

The results of testing for contamination and waste acceptance criteria are discussed in Volume 9 of this report.

Unconsolidated undrained triaxial, shear box and oedometer testing was undertaken at proposed structures and embankments where possible. Due to the limited number of undisturbed samples recovered, these tests were undertaken where suitable samples existed and were not limited to the above sites.

Limited consolidated undrained triaxial testing was carried out to determine effective stress parameters.

Acceptability of the soils was assessed using MCV, undrained shear strength, compaction tests, bulk density and moisture content tests.

All samples were appropriately labelled and stored in accordance with the Specification.

Table 4-3: Summary of Geotechnical Laboratory Testing Geotechnical Test Test Method No. Tests Undertaken

Classification/Compaction

Moisture Content BS1377: Part 2: 1990 1836

Liquid / plastic limits BS1377: Part 2: 1990 844

Bulk Density BS 1377: Part 2: 1990 8

Particle Density BS 1377: Part 2: 1990 38

Particle Size Distribution BS1377: Part 2: 1990 1153 (wet sieving method)

Determination of dry BS1377: Part 4: 1990 76 density/moisture content relationship (2.5kg rammer)

Determination of dry BS1377: Part 4: 1990 4 density/moisture content relationship (4.5kg rammer)

Geotechnical Test Test Method No. Tests Undertaken

Determination of dry BS1377: Part 4: 1990 21 density/moisture content relationship (vibrating hammer)

Recompacted California BS1377: Part 4: 1990 91 Bearing Ratio (single point)

Recompacted California BS1377: Part 4: 1990 6 Bearing Ratio (5 point)

MCV (single point) BS1377: Part 4: 1990 244

MCV Calibration BS1377: Part 4: 1990; Clause 5.5 44

Los Angeles Abrasion BS EN 1097-2: 1998 6 Value

Strength / Consolidation

Undrained triaxial (total) BS1377: Part 7: 1990 66 strength

Undrained triaxial (total) BS 1377: Part 7: 1990 24 strength (remoulded)

Shear Box (effective BS1377: Part 7: 1990; Method 4 24 strength)

Consolidated undrained BS1377: Part 7: 1990; Method 4 29 triaxial (effective) strength

Point Load Index ISRM 342

Unconfined ISRM 134 Compressive Strength

1-D oedometer BS 1377: Part 5: 1990 44

Chemical (tests on soils and groundwater)

pH, water soluble BRE 279 503 sulphate, Magnesium, Chloride TRL Report 447

Organic Matter Content BS 1377: Part 3: 1990 94

4.8.2 Copies of Test Results

Copies of all laboratory test results are included as part of the Soil Mechanics GI Reports; (Main GI Report Ref: A9101 and Preliminary GI Report Ref: Y9901).

The AGS file has been supplied on the Hard Disk drive accompanying this report which also contains the drawings and GIS model.

5 Ground Summary

Provided in this chapter of the report is a general description of the ground summary. More detailed ground summaries are provided within Volumes 2 to 8 of this report and for more information regarding the site refer to the PSSR.

5.1 Geography

Section 2 of the proposed scheme is situated within County Tyrone, in the west of Northern Ireland and extends from Sion Mills in the north (CH 27000) to the south of Omagh (CH 57600) as shown on Drawing No. 796036-0600-D- 00061B. The route was selected in July 2009 from four proposed alignments and is generally situated adjacent to the existing A5 and to the west of it.

The proposed scheme of Section 2 by-passes a number of towns and villages, the most notable of these are Sion Mills, Newtownstewart and Omagh. Sion Mills is the smallest of the three towns and is located to the east of the alignment at the northern extent of Section 2, between CH 27000 and 28500. The existing A5 runs through the centre of Sion Mills, and acts as a bottle neck for the traffic due to speed limitations. The land across which the new alignment will cross is general farmland used for arable and grazing purposes.

Newtownstewart is located approximately in the middle of Section 2, between CH 38500 and 39500, and is the second largest town that the scheme by- passes. The A5 originally continued through the centre of Newtownstewart until 2002, when a by-pass was constructed to the east of the town. The proposed scheme now by-passes the town to the west.

Omagh is the county town of County Tyrone, and is the largest town which the route by-passes. The town is located in the south of Section 2 between CH 50000 and 57000. The existing A5 runs to the west of Omagh town centre, while the proposed scheme runs through agricultural land to the west of the town outskirts.

There are a number of notable villages along the proposed scheme; these include Victoria Bridge, Ardstraw and Mountjoy. Victoria Bridge is approximately 3km south of Sion Mills, between CH 31000 and 32000. Ardstraw is approximately 5 km northwest of Newtownstewart, between CH 34000 and 34500. Finally Mountjoy is at the southern end of Section 2, approximately 5 km north of Omagh, between CH 46500 and 47000. Victoria Bridge and Mountjoy sit to the east of the proposed scheme while Ardstraw sits to the west.

5.2 Topography

The topography within the vicinity of the proposed scheme is generally dictated by the glacial environment with which it was created. Other influences include hydrological and human factors. A relief map of the topography has been provided in Drawing No. 796036-0600-D-00068B and elevations can be observed on this drawing with 10 m contours provided. Drawing No. 796036- 0600-D-00069B provides an indication of slope angles within Section 2, with a colour coded system used for ranges in slope angle.

The northern extent of the proposed scheme, between Sion Mills and the River Derg (CH 34400), is located on the western side of the Mourne valley. The elevation of the ground level ranges from between 30 m OD at the River Derg, and 90 m OD at Sion Mills. The scheme within this region is situated on gently undulating hills with slope gradients up to 1:5.

South of the River Derg, the Mourne Valley becomes the Strule Valley. The proposed scheme continues, along the western side of the Strule Valley, with a similar topography as previously discussed. The ground elevation increases as the scheme nears Newtownstewart.

To the west and south of Newtownstewart, between CH 38300 and 45600, the proposed scheme is on the lower slopes of Bessy Bell (420m OD). The ground levels increase to between 90 m and 130 m OD in this area. As the route continues south of Newtownstewart the ground slopes down to the east at gradients of between 1:4 and 1:6. The route is situated on sidelong ground through this area as it trends north to south.

The topography from the north of Mountjoy continuing south to the end of Section 2 becomes dominated by drumlins, presenting an undulating low lying terrain. The elevation of the proposed scheme remains between 60 m and 90 m OD for the southern part of Section 2, apart from some areas of elevated terrain to the west of Omagh, between CHs 53000 and 53500 and CHs 54400 and 54900, which rise to 110 m OD. The slopes, which are mainly due to the presence of drumlins, are generally between 1:10 and 1:6.

5.3 Historical Development

Historical records date back to 1830 and are discussed in more detail in the Section 2 PSSR and summarised below.

5.3.1 1830 to 1860

The existing A5 road was established prior to the earliest records, although the alignment differed slightly from the current one. Between 1830 and 1860 the Great Northern railway line was constructed, which continues the entire length of Section 2. The railway line is situated to the east of the proposed scheme apart from between CH 48200 and 49800, where the railway line is on or immediately adjacent to the route.

The proposed scheme also crosses a now redundant branch to Enniskillen at CH 55100, which is a branch of the line discussed above.

There are no other major developments within the vicinity of the preferred route. During this period the land use adjacent to the proposed scheme was mainly agricultural.

5.3.2 1860 to 1904

By 1904 there was very little change within the vicinity of the proposed scheme, other than the construction of farmsteads and associated buildings.

5.3.3 1904 to 1930

Between 1904 and 1930 the main changes within the vicinity of the scheme were associated with domestic buildings, where towns and villages have expanded into the adjacent areas. Included in this expansion is the introduction of schools, reservoirs and other developments necessary for expanding populations.

There are no notable major developments constructed between this period of time.

5.3.4 1930 to 1960

The historical data for this period is incomplete. From the available data there appears to have been no major development during this period, other than additional domestic and agricultural buildings adjacent to the proposed scheme and the gradual expansion of the town of Omagh.

5.3.5 1960 to 2007

There is very little change between 1960 and 2007 and there are no major developments. The railway line is abandoned during this period.

Immediately north of Omagh the agricultural market and the Nestle creamery were developed (east of the proposed scheme) though the latter is now disused.

5.4 Man-made Features – Mining and Quarrying

There are a number of active, backfilled and disused quarries within the vicinity of the proposed scheme.

At CH 28050 there is a backfilled quarry approximately 80 m west of the proposed scheme. There is also a backfilled quarry at CH 32600, approximately 90 m west from the proposed scheme.

Between CHs 33300 and 34000 there are 3 No. sand and gravel active quarries to the east and to the west of the proposed scheme. The quarry to the west is located adjacent to the route, while the two quarries to the east are 50 m and 150 m from the route, and they are extensively worked.

There is a large scale active quarry approximately 150 m to 300 m east of the preferred route, between CHs 36700 and 37800. Adjacent to the active quarry and to the south, there is a quarry that has been backfilled. This is approximately 150 m east of the alignment.

At CH 47500 approximately 150 m to the west of the proposed scheme is another backfilled quarry. Between CHs 53500 and 54500 both to the east and west of the proposed scheme are a number of small backfilled quarries, between 50 m and 150 m from the route.

There are no recorded landfill sites immediately beneath or adjoining the proposed scheme.

5.5 Hydrology

The scheme crosses a number of watercourses including the River Derg, Coolaghy Burn, Beltany Burn, Fairy Water and the Drumragh River. Along with those listed there are numerous minor, mainly unnamed, watercourses that the route intersects. For more information on these watercourses refer to the Section 2 PSSR.

5.6 Geology

This section will discuss the general geology across the whole of Section 2. A more detailed discussion will be presented in Volumes 2 to 8 of this report. For this section the geology will be split into two groups, superficial geology and bedrock geology.

5.6.1 Superficial Geology

The superficial geology for the area can be viewed on Drawing No. 796036- 0600-D-00078B. The superficial geology within Section 2 is dominated by glacial deposits laid down during the last glaciation of Northern Ireland, between 10,000 and 70,000 years before present. In addition to the glacial deposits is the presence of more recent alluvial and organic deposits, which occur in isolated pockets throughout the Section. These recent deposits include Peat, River Alluvium and Lacustrine Deposits/Lake Alluvium. The glacial deposits include Glaciofluvial Sand and Gravel, Hummocky Glacial Moraine and Glacial Tills.

Topsoil can be observed throughout Section 2, while there is very little presence of Made Ground. Topsoil was found to be up to 0.9 m in thickness, while Made Ground, where it was encountered, was found with thicknesses of between 0.1 m and 3.5 m. The Made Ground in Section 2 is mainly associated with the redundant railway line and isolated areas, possibly unofficial former landfill sites. Topsoil and Made Ground will not be discussed any further in this chapter as they are not considered usable for engineering purposes. Further information on Topsoil and Made Ground is provided in the Section 2 PSSR and in Volumes 2 to 8 of this report.

Peat

The proposed scheme crosses a number of peat deposits, identified from published geology and confirmed by the main ground investigation. The main ground investigation identified larger quantities of Peat deposits than was anticipated in the PSSR. The thickness of the peat encountered during the main ground investigation ranged from 0.1 m to more than 10 m and are detailed in Table 5-1 below. The specific areas of peat deposits are discussed within Volumes 2 to 8 of this report.

Table 5-1: Summary of Peat Extents CH from CH to Depth of Peat Spatial Context

30460 30610 4.5 m South of Concess Road

31450 31640 2.8 m South of Fyfin Road

40600 40700 3.3 m Castletown Road junction

46360 46520 >10.0 m North of Dunteige Road

48100 48390 1.5 m South of Rash Road

49270 49720 4.0 m Omagh North Junction

50420 50645 2.0 m Melon Park Drive

50860 51040 1.5 m North of Gillygooly Road

51350 51940 3.7 m South of Gillygooly Road

52800 53230 3.0 m Tamlaght Road

55000 55600 4.0 m North of Beagh Road

Alluvium

According to published geology and historical borehole records the Alluvium occurs in areas associated with existing or historic watercourses, predominantly in the area of the Derg, Fairy Water and Drumragh Rivers. The Alluvium is generally described in the published geology and in the historical borehole records as soft to firm brown grey laminated silt, fine sand and gravel.

The Alluvium was observed during the main ground investigation within the areas indicated by the published geology and the historical borehole records. Where it was encountered it ranged in thickness from less than a metre to 8.3 m. Deep thicknesses of Alluvium were encountered only in localised areas. The proposed scheme crosses a number of locations where the Alluvium was

identified by the main ground investigation and these locations will be discussed further in volumes 2 to 8 of this report.

Lacustrine Deposits/Lake Alluvium

From the published geology and historical borehole records the Lacustrine Deposits, formerly known as Lake Alluvium, occur along the line of the preferred route in small pockets at a few locations, north west of Victoria Bridge, west of Newtownstewart and to the south of Mountjoy. These deposits are considered to have been formed in post-glacial lake environments. From the published geology and the historical borehole records the Lacustrine Deposits are described as very soft to firm grey blue sandy silts and clays, with some organic content.

This was generally confirmed by the ground investigation, where the deposits were observed in the anticipated locations. The thickness of the Lacustrine Deposits encountered ranged from less than a metre to 5 m. Further discussion on the Lacustrine Deposits can be found in volumes 2 to 8 of this report.

Glacial Till

The Glacial Till deposits within the area of the proposed scheme are the most abundant of all the superficial deposits and are the result of the last glaciation. The Glacial Till is described in the published geology and the historical borehole records as soft to firm sandy gravelly clays and silts with cobbles and boulders present and medium dense to dense clayey silty sand and gravel. The general thickness of the deposits recorded range from 1 m to greater than 22.5 m. The maximum thickness was unconfirmed.

The Glacial Till was observed during the main ground investigation throughout Section 2 and occurs in abundance along the proposed scheme. This confirms what was anticipated from the published geology and the historical borehole records. However, the composition of the glacial till observed during the main ground investigation was found to have higher levels of granular material than anticipated. This issue will be discussed further in volume 2 to 8 of the report.

Glaciofluvial Sand & Gravel

The Glaciofluvial Sand & Gravel deposits occur throughout the proposed scheme, mainly between Victoria Bridge and Newtownstewart but also to the

north and south of Mountjoy, according to the published geology and the historical borehole records. This deposit occurs in the vicinity of current and historic watercourses, although its deposition is associated with glacial water courses. The published geology and the historical borehole records describe this deposit as silty sand and gravel with cobbles and boulders. The thickness of the deposit, as observed by the main ground investigation, ranges from less than a metre to over 7.5 m, with the maximum thickness being unconfirmed.

In the areas between CH 37100 and 39000 and between CH41250 and 42800 the route crosses over the Deer Park Deglacial Complex and the Strule Valley Deglacial Complex, respectively. These areas represent valuable resources of sand and gravel derived from the combine effects of ice and water at the end of the last ice age.

From the main ground investigation the Glaciofluvial Sand & Gravel corresponded with what was anticipated and were observed along the proposed scheme at a number of locations. The locations where the deposits were encountered also corresponded with the published geology and the historical boreholes records. Further discussion on the Glaciofluvial Sand & Gravel can be found in volumes 2 to 8 of this report.

Hummocky Glacial Morraine

The Hummocky Glacial Morraine is found in areas where the Glaciofluvial Sand & Gravel are also observed, and are associated with this deposit. Therefore, these deposits are generally encountered in the northern half of the route. The current published geology describes this deposit as Glaciofluvial Ice-contact Deposits and is formed in a similar environment to the Glaciofluvial Sand & Gravel. Published geology and historical boreholes records describe this deposit as sand, gravel and boulders with a silty sand matrix. This deposit was observed to a thickness of between less than a metre to 10.4 m, with the maximum thickness being unconfirmed.

The main ground investigation confirmed the anticipated locations of the Hummocky Glacial Moraine and it was observed within the vicinity of the proposed scheme. Refer to volumes 2 to 8 of this report for more details on this stratum.

5.6.2 Solid Geology

The solid geology is shown on Drawing No. 796036-0600-D-00077B. The underlying geology of the study area is structurally complex and falls into two

distinct provinces: Precambrian strata to the north of the Omagh Thrust Fault (OTF) and Devonian and Carboniferous strata to the south of the fault.

The OTF is a sub-horizontal thrust fault that passes through the proposed scheme at the southern limits of Section 2, immediately to the south of Omagh, between Clanabogan Road and Loughmuck Road. The OTF trends in a southwest to north-easterly direction. Precambrian strata from the north have been thrust southwards over younger Carboniferous and Devonian strata forming a large overturned fold, known as the Sperrins Nappe.

All of the solid strata encountered during the main investigation were of substantial thickness and there were no instances where the underlying solid geology stratum was recorded.

Structure – North of the Omagh Thrust Fault

North of the thrust, in the area to the west of Newtownstewart, the nappe takes the form of an asymmetric anticline, the axis of which trends from southwest to northeast. The oldest stratum at the core of the fold is the Newtownstewart Formation and is exposed in the area around Newtownstewart. The younger Dungiven Formation is exposed on either flank of the fold. Claudy Formation is also exposed on the northern flank of the fold, however, the Glenelly and Mullaghcarn Formations were not encountered. These ancient rocks form the Sperrin Mountains and Bessy Bell. Table 5-2 below summaries the strata encountered on either limb of the anticline.

Table 5-2 Summary of Precambrian Strata to the North of the OTF Age NW Limb of Sperrin SE Limb of Spatial Context Mountains Sperrins Mountain

Highland Group Highland Claudy Formation (DCCF) Not Present DCCF – Underlying the route to the northwest, Southern Southern Psammite, quartz amd near Sion Mills feldspar rich, coarse detritial grains of blue quartz and pink and white feldspar; minor

Precambrian Precambrian semipelite, limestone and Dalradian Dalradian green beds

Dungiven Formation (DUNN) Located to the northwest and southeast of the Argyll Group Group Argyll Pelite, semipelite, psammite, quartzite, Newtownstewart basaltic lava flows and volcaniclastic Formation sediments Newtownstewart Formation (DBNF) Located in the centre of the nappe, underlying the Thickly bedded quartzose psammite with thin route to the south of pelite interbeds Newtownstewart

Claudy Formation

The maximum unproved thickness of the Claudy Formation observed during the main ground investigation was 4.7 m. The thickness of the overlying superficial deposits observed during the main ground investigation was between 0.35 m and 9 m. Further details of this Formation are provided in Volumes 2 to 8.

Dungiven Formation

Superficial deposits overlying the Dungiven Formation range from between 1.4 m to over 13.25 m. The maximum thickness of Dungiven Formation observed during the main ground investigation was 9 m. Refer to Volumes 2 to 8 for further detail on this stratum.

Newtownstewart Formation

The maximum unproved thickness of the formation was 9 m. The depth of superficial cover over the Newtownstewart Formation ranged from 1 m to 14.7 m. Further information on this formation can be found in Volumes 2 to 8.

Carboniferous Outliers

Local outliers of Carboniferous strata have been faulted and sit unconformably on the Precambrian strata located to the north of the OTF. Immediately to the north of the OTF the route crosses Ballyshannon Limestone Formation.

Approximately 3 km north of the OTF, and trending in a similar direction, is the Cool Fault. Along the north of this fault the route crosses Claragh Sandstone Formation which sits unconformably on Precambrian strata. A further fault is noted to the south of Victoria Bridge and trends from east to west. On the north side of this fault, Owenkillew Sandstone Group strata of Carboniferous age lie unconformably on Precambrian strata. Details of these strata are provided below in Table 5-3.

Table 5-3: Carboniferous Stratigraphy South of the Age Omagh Description Spatial Context Thrust Fault

Ballyshannon Immediately north of Limestone Limestone, dark bluish grey; silty the OTF, near to Formation mudstone, fossilferous; rare chert Clanabogan Road (BAL) Visean

Sandstone, very coarse grained, fine North of the OTF from

Claragh conglomerate, fawn and grey, arkosic; Killinure Road to the Sandstone thin limestone; grey mudstone with Fairy Water and from Formation Carboniferous micropores Gillygooly Road to Palaeozoic (CLSG) Brookmount Road

Owenkillew Greenish grey and purplish red North of the OTF from Tournaisian

Sandstone sandstone and siltstone with thin beds Seein Road to Stone Group of algal laminated limestone. Dark Road (OWSA) grey mudstones contain microspores

Omagh Red sandstone with calcrete nodules North of the OTF, from

Visean Visean Sandstone and pebbles of white quartz. the Fairy Water to Group Gillygooly Road (OMSG)

Ballyshannon Limestone Formation

Where Ballyshannon Limestone Formation was observed there was between 5.3 m and 6 m of overlying superficial deposits. The maximum thickness of the rock observed during the main ground investigation was 5.5 m. Further information of this unit can be found in Volumes 2 to 8.

Claragh Sandstone Formation

Where Claragh Sandstone Formation was observed there was between 3 m and 13.5 m of overlying superficial deposits. The sandstone was proven to 5.2 m. Refer to volumes 2 to 8 for further details on this formation.

Owenkillew Sandstone Group

Where Owenkillew Sandstone was proved there was between 5 m and 20.5 m of overlying superficial deposits. The maximum proved thickness of Owenkillew Sandstone observed during the main ground investigation was 5.0 m. Refer to Volumes 2 to 8 for further details on this stratum.

Omagh Sandstone Group

Where this unit was observed it was found to be overlain by between 7.5 m and 13.5 m of superficial deposits. The sandstone was proven to 5.0 m during the main investigation. Refer to Volumes 2 to 8 for further details on this group.

Structure – South of the Omagh Thrust Fault

To the south of the OTF the strata is a large fault block of Devonian age Shanmullagh Formation which is described as sandstone and mudstone

Details of the Shanmullagh Formation recorded across the southern part of Section 2 are shown below in Table 5-4.

Table 5-4 Strata to the south of the Omagh Thrust Fault South of the Age Omagh Thrust Description Spatial Context Fault

Brown coarse grained pebbly sandstone, Covers the Section 2

UpperDevonian Shanmullagh thin purplish grey fine-grained sandstone route from the OTF

Palaeozoic Formation and mudstone. Also consists of purplish southwards grey sandstone and mudstone laminae (red sst & mudst) with ripples. Sandstone also in channels (SHAN) (up to 2 m deep) & consists of sand siltstone, reddish brown mudstone.

Shanmullagh Formation

Superficial deposits overlying the Shanmullagh Formation were observed at between 4 m and 13.2 m in thickness. The sandstone was proven to 5.35 m. Refer to Volumes 2 to 8 for further details of this Formation.

5.7 Hydrogeology

5.7.1 Hydrogeology within the Superficial Deposits

A number of superficial aquifer deposits are recognised within the route corridor. These are typically glacial sand and gravel and granular alluvial deposits, and are generally associated with the major watercourses along the route, such as the Strule. These alluvial deposits are classified as superficial aquifers supporting intergranular flow.

Additional superficial deposits, classified as non-aquifers, are present along the route corridor. These include cohesive and granular glacial till, moraine and peat deposits. Some areas of alluvium are composed of organic clay or more cohesive deposits, giving them a much lower permeability than the granular alluvium and meaning they are considered to be non-aquifers. Some areas have been identified where superficial deposits are thin or absent.

Further discussion on the hydrogeology of the superficial deposits can be found in the Section 2 PSSR and in Volumes 2 to 8 of this report.

5.7.2 Hydrogeology within the Bedrock Geology

The Hydrogeological Map of Northern Ireland is shown on Drawing No. 796036-0600-D-00079B. The Precambrian strata underlying the northern part of the proposed scheme is classified as having ‘fracture flow, of limited

productivity, Bl(f)’. These aquifers are capable of producing high to moderate yields in places, although their dependence on fracture flow also makes poorer yields likely. There is some potential for regional flow, although local flow is more significant. These strata are capable of providing small domestic or farm supplies and may provide baseflow to local streams and ponds.

The Carboniferous rocks, around Victoria Bridge and Omagh, are dominated by sandstones and have been classified as ‘fracture flow, of moderate productivity, Bm(f)’. This indicates that these strata have the possibility of higher yields than the Precambrian bedrock, although the predominance of fracture flow also indicates that low yields are possible.

South of the Omagh Thrust Fault, the bedrock is composed principally of Devonian sandstones and mudstones. These have been assigned an aquifer classification of ‘fracture flow, of moderate productivity, Bm(f)’. These strata are dominated by fracture flow, but also have some possibility of porous flow although yields are still likely to be variable.

The presence of groundwater in the bedrock was confirmed by the main ground investigation. Further discussion on the hydrogeology of the bedrock can be found in the Section 2 PSSR and in Volumes 2 to 8 of this report.

5.7.3 Groundwater Vulnerability

Groundwater vulnerability for Northern Ireland is classified on a five-point scale from 1 (Low) to 5 (Most Extreme). Class 4, which has the largest spatial coverage, has been subdivided into classes 4a to 4e, depending on the type of superficial deposit present. This summary has not taken account of this subdivision, although details are included within Chapter 12 of the Environmental Statement, Geology & Soils.

Groundwater vulnerability along Section 2 of the A5WTC has been classified as varying between Class 4 (Extreme) and Class 2 (Moderate). The northern part of the scheme, from Sion Mills to Mountjoy, is dominantly classified as 4 (Extreme). Areas of Class 2 are associated with 3-10 m thick low permeability Lake Alluvium and Glacial Till in the Victoria Bridge area.

The southern half of the scheme is dominated by groundwater vulnerability Class 2. Vulnerability Class 2 dominates the area from Mountjoy, south to the end of Section 2. This is largely a result of the extensive low permeability superficial deposits, mostly glacial tills, moraine deposits or peat. Areas with high permeability superficial deposits have been assigned Class 4 to reflect this; these consist largely of River Alluvium and Glaciofluvial Sand and Gravel.

5.8 Geomorphology

The most significant geomorphologic features within Section 2 are drumlins which dominate the landscape of the southern half of the section. Drumlins are glaciation features which form as ice moves over the underlying till and reshape it into elongated hills. Due to the depositional nature and layering within drumlins there can be decreased soil strength and friction characteristics in certain directions which can lead to slope instability in some cases. This will be discussed in more detail in Volumes 2 to 8.

6 Ground Conditions and Material Properties

6.1 Introduction

The route has been split into sub sections based on geography and geological/geotechnical similar areas. Ground conditions and material properties for each of these sub sections will be discussed in detail in Volumes 2 to 8.

This volume contains background to correlations and interpretations used in assessing material properties.

6.1.1 Definition of Parameters

In this Ground Investigation Report (GIR) material properties have been given in terms of Derived Parameters in accordance with Eurocode 7. A Derived Value is a "value of a geotechnical parameter obtained by theory, correlation or empiricism from test results” (Ref. EN 1997-1 Cl 1.5.2.5)

Characteristic Values have not been defined in the GIR as they are defined in Cl 2.4.5.2(3) of EN 1997-1 as: “The characteristic value of a geotechnical parameter shall be selected as a cautious estimate of the value affecting the occurrence of the limit state”. These values are selected with regards to the limit state that is being designed for, and the structure that is being designed and their selection is therefore part of the design process and is to be discussed in the Geotechnical Design Report (Ref. Mouchel internal EC7 advice memo, February 2010).

Geotechnical Derived Parameters to be taken forward to the Geotechnical Design Reports have been derived from:

• The results of geotechnical laboratory testing

• Established correlations using the results of the laboratory testing and insitu testing.

• Where no field or laboratory data was available geotechnical parameters were estimated from published reference data.

This volume includes a discussion of the various correlations and published data used for the analysis. A discussion of results of the laboratory and insitu testing will be included for the relevant sub sections in Volumes 2 to 8, together with the recommended Derived Parameters.

6.1.2 Correlations used for use with both Cohesive and Granular Material

The following correlations are suitable for both cohesive and granular soil and are used in the production of this report although not every correlation will be used in every sub section.

6.1.2.1 Coefficient of Horizontal Consolidation (c h )

Derived from measurement of the dissipation of pore water pressure dissipation in the static cone penetrometer test and the following chart.

Figure 6-1: ch values derived from t 50 values (after Robertson et al 1992)

Note: In the absence of other data the central rigidity line should be used.

6.1.2.2 Coefficient of Vertical Consolidation (c v )

The ratio of c h /c v is normally between 1 and 2 (Ref Craig, 2004).

Bergado, 1994 gives the ratio as c h=(k h / k v) cv with the k h / k v ratio varying with the fabric of the soil in accordance with the following table.

Table 6-1: Range of Field values of k h / k v ratio (after Bergado et al 1994)

6.1.2.3 Dynamic Probe Correlations

Dynamic probes used on site were limited to Dynamic Probe Super Heavy (DPSH) B, as defined in Geotechnical investigation and testing -- Field testing -- Part 2: Dynamic probing (Ref. EN ISO 22476-2:2005), and Mackintosh Probing).

There are a number of correlations relating DPSH N 100 to SPT N values, e.g Cearns P.J. and McKenzie (1988). Warren, 2007, Spagnoli, 2008 and Card et

al, 1990. Some of these use factors to relate individual N 100 to SPT N values

while others sum groups of three consecutive N 100 values to obtain an equivalent N Value. i.e:

N= N 100 + N 100 + N 100 Equation 6-1

The relationship is only linear between 5 ≤ N 100 ≤13 and equivalent N values greater than 50 will only be reported as N>50.

The summation technique is taken as the standard for the A5WTC Ground Investigation however if any variations are used, for examples derivations based on actual field data, these will be discussed in the individual sub sections.

Mackintosh Probes were used in areas of bad access where typically the ground conditions were not suitable for wheeled or tracked vehicles.

Correlations with N Value and Undrained Shear Strength are (Both Ref. Fakher et al, 2006):

N = 0.15M 0.96 Equation 6-2

cu =2.5M (NB Limited to cu <50 kPa) Equation 6-3 Where M= blows/100mm

6.1.2.4 Permeability (k)

Where field data is not available an approximation of permeability can be obtained using the following table:

Table 6-2: Typical permeability values for Soils (Carter and Bentley, 1991)

Care must be taken that permeability quoted must be for the whole soil unit as granular and more sandy layers in the till will have significantly greater flows than the more cohesive layers.

6.1.2.5 Young’s Modulus (E)

Where not directly measured, Young’s Modulus has been calculated using the following formula (Ref. IAN 73/06):

E=17.6(CBR) 0.64 MN/m 2 Equation 6-4 Where CBR= Californian Bearing Ratio and is given as a %.

E will be E’ or E u dependant on whether the CBR values are equilibrium values derived from PI results or undrained values derived from insitu tests.

Stroud and Butler, 1975 have also developed empirical correlations relating Eu

to cu .For glacial clay (Plasticity index=10-20%) this is:

Eu=300 cu Equation 6-5

6.1.3 Correlations used for use with Granular Material

The following correlations are suitable for use with granular material. Throughout the investigation assessments have been made to determine the whether a granular material with a fine grained matrix acts in a cohesive or a granular manner. The general case is that when the fines content exceeds 15%, the soil will behave as a cohesive soil when handled in an earthwork though when assessing foundation material this percentage is 35%.

6.1.3.1 Phi ( φφφ' ) and Relative Density

Peck et al established a relationship between N Value, phi and relative density

Figure 6-2: Relationship between N value, Phi and Relative Density (after Peck et al, 1967)

6.1.3.2 Phi ( φφφ' )

From BS8002 Cl2.2.4 the estimated peak effective angle of shearing resistance can be calculated from:

φφφ' max = 30+A + B + C Equation 6-6 And the estimated critical state angle of shearing resistance is given by:

φφφ' crit = 30+A + B Equation 6-7 Where: A= angularity of the particles

B= grading of the sand/gravel

C= results of the standard penetration test A, B and C are defined in defined in Table 6-3.

Table 6-3: φφφ' for Siliceous Sands and Gravels

6.1.3.3 CPT Cone Resistance, N Value and φφφ' Relationships

There is an argument that angularity and grading are inherently incorporated into SPT resistance and hence the N value already reflects the A, B and C variables given in Table 6-3. Figure 6-3 (Ref. Barnes, 2000) therefore shows

an alternative relationship between N and φ' and also includes a relationship

between cone resistance (q c) (from CPTs) and φ' .

Figure 6-3: Relationships between angles of internal friction and insitu tests

6.1.3.4 Relative Density from CPT Cone Resistance

Relative density of granular soils, φ‘, drained Young’s modulus and equivalent N Values, can be determined from cone resistance using Table 6-4:

Table 6-4: Relationship between Cone Resistance, Phi and Young’s Modulus (Ref. Eurocode 7)

Eurocode 7 also has a formula to determine φ' directly from the cone resistance:

φφφ' =13.5 x Log q c + 23 Equation 6-8 This relationship is however only valid for uniformly graded (coefficient of uniformity <3) sands which are above the water table and have a cone resistance in the range 5 to 28 MPa.

6.1.3.5 Equivalent N Values from CPT Cone Resistance

Although it is recommended that the cone resistance is used directly to calculate pile capacity etc directly, equivalent N values can be determined from Figure 6-4: CPT N Value Correlation (Ref. www.conepenetration.com/online- book).

Figure 6-4: CPT N Value Correlation

6.1.3.6 Allowable Bearing Capacity from N Values

Terzaghi and Peck developed a technique for calculating allowable bearing pressures. This was subsequently developed by Peck, Hanson and Thorburn, 1974. This method cannot be used for design of Category 2 and 3 structures under Eurocode 7 as it circumvents the use of Partial Factors to determine design values for ultimate bearing pressure. It can, however, be used for Category 1 structures as these can be designed using “empirical methods”. To this end Figure 6-5 replicates the revised method in graphical form (Ref. Barnes, 2000).

Figure 6-5: Terzaghi and Peck method for Calculating Allowable Bearing Pressure

6.1.4 Correlations used for use with Cohesive Material

The following correlations are suitable for use with cohesive material. A number of these are derived from consistency indices, i.e. moisture content and liquid and plastic limit tests, which provide a useful correlation with soil strength and stiffness indices (Ref BS 8002).

The plasticity index is defined as:

Ip = LL-PL Equation 6-9

Where Ip=plasticity index, LL=Liquid Limit and PL= Plastic Limit

The liquidity index is defined as:

LI=(w-PL)/Ip Equation 6-10

Where LI= liquidity index, w= moisture content

6.1.4.1 Phi

A method of determining φ' peak , and φ' residual from plasticity data was developed by Gibson, 1953 and is shown graphically in Figure 6-6.

BS8002 also tabulates a method of determining φ' crit from plasticity data. This is shown in Table 6-5 and also shown graphically in Figure 6-6, together with

φ' peak , and φ' residual . If the material being tested contains sand or silt then the next value of the plasticity index shown in Table 6-5, higher than recorded in the tests should be used unless it is certain that only the clay itself has been tested. For PI values less than 15˚ the peak and residual lines have to be projected back.

Where possible all three phi angles will be quoted. The peak stress relates to conditions to the stress state in the ground and can be used for serviceability state calculations where low strains are anticipated. Under limit state calculations, for example where failure is occurring, the stress conditions are

governed by φ' crit values. These values may also occur when movement has

occurred, due to water softening and/or swelling. Residual φ' residual values should be used when modelling slopes where failure has already occurred. First time slides due to new construction, however, have been found to mobilize

mass strengths no lower than φ' crit (Ref BS8002).Earthworks can undergo large deformations, however, before the peak shear strength is mobilized and failure takes place (Ref. BS 8031). New earthworks, which have not failed, should therefore be modelled using peak strengths.

Figure 6-6: Angle of Internal Friction Determined from Plasticity Index

Phi Angle from PI data

φ' peak 20

15 φ' critical

Angle Shearingof Resistance (Degrees) φ' residual

5 φ' peak and residual from Gibson φ' critical from BS8002

0 0 10 20 30 40 50 60 70 80 90 100 110 120 Plasticity Index (%)

Table 6-5: Critical Angle of Internal Friction from Plasticity Index (BS 8002)

6.1.4.2 Undrained Shear Strength, c u

It has been found to be extremely difficult on the A5WTC to obtain undisturbed samples of glacial tills due to the gravel and cobble content. Therefore direct measurement of undrained shear strength has been significantly constrained. In consequence, use of correlations to other properties is of high importance. Undrained shear strength (Cu) values can determined using correlations with SPT N Values, plasticity data and, where possible, cone penetration data.

Stroud and Butler, 1975 determined that Cu values can be determined from N values using the following equation:

2 cu=f 1N (kN/m ) Equation 6-11

Where f 1 varies with Plasticity Index in accordance with plasticity as shown in Figure 6-7.

Figure 6-7: Variation of f1 with Plasticity Index (after Tomlinson, 2001)

Whyte, 1982, determined a direct correlation for the undrained shear strength of remoulded clays using plasticity data using the formula:

(4.23(1-LI)) 2 cu=1.6e (kN/m ) Equation 6-12 Where LI= Liquidity Index.

Care has to be taken using this formula with overconsolidated soils as there are some arguments that the shear strength for these materials becomes

independent of plasticity. Any c u values derived for overconsolidated soils, using this method, should therefore be treated with caution and assessed alongside other data.

Craig, 2004 gives another correlation for cu for normally consolidated clays relating Cu to effective vertical stress and plasticity index:

cu=(0.11+0.0037I p). σ’v Equation 6-13

Where: σ’v= effective vertical stress and I p is plasticity index.

For overconsolidated clays Chandler, 1988 modified Equation 6-13 as follows:

cu =(0.11+0.0037I p). σ’c Equation 6-14

Where: σ’c=pre consolidation pressure and I p is plasticity index.

Ladd et al 1977, had the following approximation for overconsolidated clays:

Log c u = 0.2 + 2.0I L Equation 6-15

Undrained shear strength has also been calculated from the results of the cone penetration testing using:

2 cu =q c/N’ K (kN/m ) Equation 6-16 (Ref. http://www.conepenetration.com/online-book)

Where q c= measured cone resistance and N’ K is the effective cone factor. This is taken to be 20 for over consolidated clays and 18 for normally consolidated clays for the cones used during the investigation.

It is recommended that the undrained shear strength is calculated using as many of the above combinations as possible and an assessment made of suitable derived parameters following an assessment of all the data in combination.

6.1.4.3 Co-efficient of Volume Compressibility (m v)

For the same reason as undrained shear strength, it has proved difficult to

measure the co-efficient or modulus of compressibility (m v) on the A5WTC.

Stroud also developed a relationship between the N value and mv which can be used.

2 mv=1/(f 2N) (m /MN)

where f 2 varies with plasticity as shown in Figure 6-8.

Figure 6-8: Variation of f2 with Plasticity Index (after Tomlinson, 2001)

6.1.4.4 Young’s Modulus (E)

Skempton and Bjerrum, 1957 have determined that E (Young’s Modulus or the

elasticity of the soil) can be related to m v using the following relationship:

E’=1/ mv Equation 6-17 Using the Stroud correlation this can therefore be related to N value using the following equation.

2 E’= f 2N (MN/m ) Equation 6-18

6.1.4.5 Compression Indices

Although m v values are widely quoted they do vary with applied surcharge. Compression indices, which are independent of surcharge, are therefore often additionally quoted. There are a number of correlations based on plasticity data, which are used to determine these parameters. These are used in the production and are quoted below.

Compression Index (C c)

Cc is the gradient of the linear portion of the e – log σ’ graphs from oedometer tests and is calculated using the following equation (after Craig, 2004):

Cc = (e 0- e 1)/log( σ’1/ σ’0) Equation 6-19

Gregory and Bell, 1991, proposed the following relationship specifically for Belfast tills which are likely to analogous in properties to tills in the area of the A5. This is similar to an earlier correlation proposed by Skempton, 1944.

Cc=0.004(LL-5) Equation 6-20

Wroth and Wood, 1978 also developed a relationship between C c and specific gravity for remoulded soils using the following equation.

Cc= ½ I p.G s Equation 6-21

Where I p = plasticity index and G s= specific gravity.

NB in this equation I p is expressed as a ratio (e.g. 15/100) not as a percentage.

Although the compression index is difficult to estimate for peat, Hobbs, 1986 gives the following correlations from moisture content.

Cc=0.0065.w for bog peats Equation 6-22

Cc=0.008.w for fen peats Equation 6-23 Where w=natural moisture content as a %

In this instance, bog peat are upland deposits laid down in areas where precipitation exceeds evaporation (i.e. blanket bog) whereas fen peat tend to be low lying peat formed in areas of poor drainage. It is considered that the peat encountered during the investigation, typically inter drumlin deposits and raised peat bogs, are both fen deposits so the second of the two correlations applies. It should be noted, however, that the correlation would typically only apply to the main anaerobic zone of the deposit (catotelm layer). Near surface deposits (acrotelm layer) tend to be drier and have some tensile strength. Organic matter decays more rapidly in the catotelm layer. (see also secondary compression below).

6.1.4.6 Re-compression Index

The recompression index (C r) or swelling index (C s) relates to the unloading phase of a 1D consolidation test and is typically used to model the re-

compression of over consolidated materials at stresses less than the pre consolidation pressure.

Gregory and Bell, 1991, have the following relationship for Belfast tills:

Cr= 0.0015LL Equation 6-24 Once imposed stresses exceed the pre-consolidation pressure (see below) the consolidation of the soil is governed by the Compression Index.

6.1.4.7 Secondary Compression Index

Secondary compression occurs when the excess pore water pressure imposed by any surcharge has dissipated. However, compression of the soil continues. This is of particular note in organic soils. The exact mechanism for this is not known but may be due to rearrangement of particles on a very small scale and / or decay of organic particles. The co-efficient of secondary compression index

(C α) is analogous to C c but is measured using change in time on the secondary compression part of the loading curve, rather than change in stress.

Cα = (e 0- e 1)/log(t1/ t 0) Equation 6-25 (after Carter and Bentley, 1991)

Tomlinson gives the following correlation between Cα and moisture content for clays.

Cα = 0.00018.w Equation 6-26

6.1.4.8 Pre-consolidation Pressure (p c’)

The pre consolidation pressure is the maximum amount of stress that a soil has been subjected to in the past. For example for glacial till this may be the stress imposed by the glacier, which has now been released. As the till acts in a plastic manner rather than an elastic mechanism it retains a “memory” of this previous stress and is termed over consolidated. As discussed above consolidation that occurs due to imposition of new stresses below the pre consolidation pressure is controlled by the recompression index, whereas consolidation above the pre-consolidation pressure is controlled by the compression index. The pre consolidation pressure can be calculated with odometer tests, using the Casagrande method given in Craig, 2004 and also using a correlation with plasticity data, which is a re-arrangement of Equation 6-

11. Note the accuracy of this formula is +/- 25% and the formula is not valid for sensitive or fissured clays.

σ’c= cu/(0.11+0.0037I p). Equation 6-27 (After Chandler, 1988)

Where Ip= Plasticity index and c u is a measured value

6.1.4.9 Overconsolidation Ratio

The over consolidation ratio (OCR) of a soil is the ratio of the maximum effective stress in the past to the current value. A normally consolidated soil would have a ratio of unity. This can be related to the undrained shear strength with the following correlation:

1.25 OCR=[( cu / σ’v)/0.25] Equation 6-28 (Adaption of formula from Ladd et al, 1977)

Typical values for OCR are given in Table 6-6.

Table 6-6: Overconsolidation Ratios (After Barnes, 2000) Soil Type OCR

Normally consolidated 1

Lightly overconsolidated 1.5 - 3

Heavily overconsolidated >4

6.1.4.10 Permeability (k)

For a uniform cohesive soil, permeability is inherently linked with consolidation properties as these relate to the dissipation of excess pore water pressure. Craig, 2004, therefore gives the following relationship.

Cv=k/(M vγw cu ) Equation 6-29

Where k= co-efficient of permeability (m/s) and γw is the unit weight of water which= 9.81kN/m 3 .

Extreme care will be taken in the reports when quoting derived values for permeability, to ensure that there are no sandy/more permeable horizons which would dramatically increase the permeability of the overall unit.

The co-efficient of permeability has also been calculated from permeability testing carried out during the ground investigation and in installations installed as part of the investigation.

6.1.4.11 Californian Bearing Ratio (CBR)

Californian Bearing Ratio has been determined directly using field testing and laboratory testing on soaked and unsoaked samples.

IAN 73/06 Rev 1 indicates that the pavement design should be based on the lower of the long term and short term CBR values. Short term values are derived from the field and laboratory testing whereas long term values for cohesive materials are derived using the soil suction method and PI values. A summary of the results of the soil suction method is given in Table 6-7, which is

derived from IAN 73/06. A simplified version of this table is given in IAN 73/06 Rev 1 but it is considered that this table is more useful.

Table 6-7: Equilibrium Subgrade CBR Estimation

Notes: 1. A high water table is 300mm below formation or subformation 2. A low water table is 1000mm below formation or subformation 3. A thick layered construction is a depth to subgrade of 1200mm 4. A thin layered construction is a depth to subgrade of 300mm

For cohesive soils the undrained or short term CBR can also be estimated using the Black and Lister, 1978 correlation with undrained shear strength where:

CBR=Cu/23 Equation 6-30 If the Young’s Modulus of the soil is known the short term CBR can also be determined from:

E=17.6(CBR) 0.64 Equation 6-31 (From IAN 73/06 Rev 1)

6.1.5 Correlations used for use with Rock

6.1.5.1 Unconfined Compressive Strength

Due to the nature of the rock a large number of point loads have been carried out compared to Unconfined Compressive Strength (UCS) tests.

Point load results can be converted to UCS values using the equation:

σcf =CI s Equation 6-32 (from Farmer, 1983)

Where σcf = UCS, I s= the point load index and C= a constant

Where sufficient data exists in one area C will be calibrated on site but where

this is not possible a value of 23 will be used for 50mm core (To which the I s have generally been standardised)

6.1.5.2 Rock Parameters for Failure Analysis of Cut Slopes

In areas of rock cut where joints are widely spaced the stability of the slope will

be controlled by joint orientation and sliding resistance on discontinuities ( Фb). Joint orientation will be discussed in the chapters on the design of the individual rock slopes however suggested values for sliding resistance are given in Table 6-8 which is based on work by Barton and Choubey, 1977.

Table 6-8: Basic friction Angle on Discontinuities (after Barton and Choubey, 1977)

Rock Type Typical Range, Фb Proposed Design Value

Фb

Limestone 31 -37 34

Shale 27 27

Siltstone 21-33 32

Sandstone 26 - 33 31

Note the friction angles should be reduced if there is any infilling on the joint surfaces.

The shear strength along the discontinuity is then calculated using:

Τf=σ’ntan( Фb+JRC log (JCS/ σ’n) Equation 6-33 (after Barton, 1971)

Where:

Τf= shear resistance along the discontinuity; σ’n= effective stress

normal to the discontinuity; Фb= basic friction angle, JRC is a joint roughness co-efficient (Ref. Barton & Choubey, 1977) and JCS is the uniaxial compressive strength of the rock in the joint wall)

JRC can be determined from Figure 6-9.

Figure 6-9: Joint Roughness Co-efficient (After Barton & Choubey, 1977)

The shear resistance value will be used in with detailed analyses of the joint spacing and orientation for particular cutting slopes to determine overall cutting stability. This analysis will be discussed in the relevant sections in Chapter 8.

In a heavily jointed rock mass the controlling failure mechanism will be circular failure using effective stress parameters (c’ and φ’) determined for the whole rock mass.

Hoek and Diederichs, 2006, have developed an empirical formula which relates

Rock Mass Modulus (E rm ) to the Intact Rock Modulus (E i), the Geological Strength Index (GSI), and a Disturbance Factor. The latter varies with type of

cut, height of slope etc. The following formula calculates E rm .

1− D 2/ Erm = Ei 02.0( + ) Equation 6-34 1+ e (( 60 +15 D−GSI 11/) )

Where Erm = Rock Mass Modulus, D= Disturbance Factor, GSI=Geological Strength Index and e is the mathematical function.

For civil engineering works D=0.7 for Good Blasting and 1.0 for Poor Blasting.

The RocScience freeware programme RocLab (Ref. www.rocscience.com )

calculates E rm . using both field data and suggested correlations. The programme then calculates the equivalent Mohr-Coulomb parameters, from the Hoek-Brown failure envelope, giving initial c’ and φ' parameters which can be used in circular sliding failure calculations for heavily fractured rock.

Again the stability of individual slopes will be discussed in the relevant section of Chapter 8.

An alternative method of determining the rock mass modulus using UCS, fracture index and RQD values was developed by Hobbs, 1974. This used the following relationship:

Erm =j.M rquc Equation 6-35

Where j=rock mass factor; M r=modular ratio and q uc =unconfined compressive strength.

Modular ratio values and rock mass factors are given in Table 6-9 and Table 6-10 respectively.

Table 6-9: Modular Ratios (After Hobb’s 1974)

Table 6-10: Rock Mass Factors (After Hobbs, 1974)

6.1.6 Conclusions

Derived parameters for individual sections of the route, calculated using a combination of the correlations described above, laboratory results, insitu tests and field descriptions, will be described in subsequent volumes of this report. All available permutations of the above will be used to determine the most representative parameters.

7 Geotechnical Risk

Refer to Volume 10

8 Basic Design Philosophy and Methodology

8.1 Introduction

In developing the scheme to a specimen design used to develop alignments, structures, vesting and direction orders and a cost estimate, some outline geotechnical design work has been required. Although geotechnical design of the scheme is the subject of the Geotechnical Design Report (GDR), the purpose of that report is to record the detailed design of the scheme. Therefore, although beyond the scope of HD22/08, those outline designs are recorded here and should be developed by the detailed design organisation.

A number of common design philosophies have been developed for use across the scheme in order to provide best value for the scheme. These Principles have been developed using experience and knowledge of the ground conditions and engineering properties of material encountered on other projects within the area and are described in this chapter.

The designs have been refined as necessary to suit site specific conditions and were modified as described are described in the appropriate sections in Volumes 2 to 8.

8.1.1 Earthworks Definitions

For avoidance of doubt the following definitions have been used throughout the scheme:

Cuttings are when both sides of the earthwork are in excavation. They may be asymmetric so the depth shown on the centre line long section may not show the full height.

Embankments are when both sides of the earthwork are in fill. They may be asymmetric as above.

Side long ground is when one side is in cut and the other on embankment. The centre line long section will certainly not show the full earthwork height here and you may need cross sections too. Because of groundwater issues, and changing the slope loading, these can be particularly sensitive to slope stability, often requiring a shallower slope.

Earthworks <1.5m in height are considered to be “at grade” and don’t usually have slope stability issues. However, if an earthwork exceeds 1.5m at any point, then the full length back to ht = 0 becomes part of a cutting or embankment.

8.1.2 Groundwater

The groundwater levels will be assessed in the individual sub sections. In general the highest recorded level plus 1m will be adopted as the design level, unless site specific conditions or ground level dictate otherwise. This would be equivalent to the Ultimate Limit State under EC7 which requires highest possible water levels.

8.2 Earthworks

8.2.1 Cutting stability

Soil Slopes

The stability of slopes is a function of:

• Soil type

• Undrained shear strength (c u) for short term conditions and

• Drained inter-particle friction ( φ’) and drained cohesion (c’) for long term conditions.

• Slope gradient

• Slope height

• Groundwater level

• Surcharges

An HB loading of 20 kN/m 2 has modelled throughout on the footprint of the road with a surcharge of 10 kN/m 2 on verges and above the slopes to model agricultural traffic and the like.

With respect to baseline cutting slope analysis, effective parameters of c '=1 and φ'=30 0 have been employed for modelling slopes in cohesive soil and a c'=0 and φ'=36 0 used for granular material. This figure is considered appropriate as in general any failures induced will be first time slides and hence peak shear strength parameters can be used (Ref. BS8004). If pre existing

failures are encountered residual values will be modelled with a c r’ of 0.

Modelling has been carried out to determine what angle of slope is required to achieve a safe angle of slope with varying slope height and depth to ground water table. As first time slides were being considered a factor of safety of 1.3 was required for deep seated slip circles.

This analysis determined that generally slopes up to a maximum height of 10 m were stable with a slope angle of 1 vertical (v): 2.5 horizontal (h), providing that the groundwater is at least 1 m below surface. A discussion on drainage design is detailed below.

Slopes greater than 10 m high will require a berm, at mid height, of at least 2 m wide to maintain stability. The berm should slope outwards at a minimum crossfall of 1:20 so as to shed any trapped water.

Rock Slopes

The stability of rock slopes in which the rocks are moderately weak or weaker are largely controlled by a combination of the rock strength and the orientation and shear strength properties of the discontinuities. In higher strength rocks the stability of the slope is mostly controlled by discontinuities within the rock (Ref. Harber et al, 2000).

The Harber et al paper states that between the 1930s and the 1970s the majority of rock slopes were constructed with slope angles of 3v or 4v:1h without much regard to the local geology or discontinuities. Slopes of these angles, which did not have some form of inbuilt stability protection, invariably required later remediation and maintenance during their design life.

To avoid this requirement slope design now requires due consideration of discontinuity orientation and rock strength for moderately weak and weaker rocks and discontinuity orientation only for stronger rocks, provided their vertical height does not induce vertical stresses greater than the strength of the rock.

On the A5 the propensity of the Dalradian shale and schist rocks to decay to a scree slope and the potential for weathering of the Carbonifereous sandstones

means that slopes steeper than 1v:1h have not been recommended as the norm unless further detailed further analysis has been carried out.

For rocks moderately strong and stronger an analysis of the joint orientations has been carried out with stereonets in packages such as Dips to determine the controlling joint orientations and hence the safe angles of slope.

For rocks slopes with a strength of moderately weak or weaker the safe angle of slope has been determined using shear strength properties of the rock mass (using soil mechanics methodology) and an analysis of the discontinuities. The shear strength properties has been determined by use of software packages such as RocLab or Bieniawki’s Rock Mass Rating (RMR) which is reproduced in Table 8-1 where the RMR is determined by summing Rows 1, 2, 3 ,4, 5 on Table 8-1 and then subtracting a value corresponding to the joint orientation (Row (b)). The shear strength properties (c ' and φ‘) can then be determined from the RMR using Row (d).

Where the analysis indicates that rock slopes steeper than 1v:2h are permitted than the following additional measures will be required:

• Boulder trenches at the toe of the slope to catch falling debris. For initial design purposes this it is recommended that this is 1 m wide for every 1 m height of slope, up to a maximum width of 4 m. More detailed design of the rock catch ditches can be carried out using methods such as that given on Figure 8-2.

• At 10 m intervals a 4 m wide berm will be required to catch falling debris. This should either be horizontal or slope inwards towards the rock face. Harber et al state that a berm’s effectiveness can be increased by the placement of energy absorbing material such as peat on the berm’s surface.

• If the rock slope is overlain by drift deposits a 4 m wide berm is recommended at the interface, with a drainage ditch to intercept any surface run off and groundwater in the drift deposits. The berm can be reduced in width to 2 m for rock slopes <4 m high. The safe angle of slope for the drift deposits will also have to be determined.

• If a rock slope is of a low height consideration will be given as to whether to treat it as a soil slope with a slope angle of 1v:2.5h as this may require less land take than a slope incorporating boulder trenches. For example for a rock face that is stable at a slope of 1v:1h, less land take is required up to a height of 4 m to construct the slope at an angle of 1v:2.5h without a boulder trench rather than construct it at 1v:1h with © Mouchel 2010 80 718736-0600-R-007 Vol 1 of 10 - August 2010 A5 WTC - Section 2 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

a boulder trench, which will be up to 4 m wide. Above 4 m height less land take is required if the slope is constructed at 1v:1h with appropriate remedial measures. This relationship is shown in Figure 8-2.

Table 8-1: Geomechanics Classification of Jointed Rock Mass (after Bieniawski, 1976)

Figure 8-1: Guidelines for the Design of Rock Traps (After Whiteside, 1986)

5 2.0 H 1.5 βββ D 30

W 4

1.25 Key 20 D

3 W Slope height, H (m) height,Slope H

10 2

1.0

1 0 90 80 70 60 50 40

Slope angle, βββ (degree )

Figure 8-2: Rock Slope Land Requirements

Cutting land take requirement

12 w idth of boulder 10 trench 8 w idth of boulder slopeht trench mid berm reqd 6 w idth reqd 1:1 w ith 4 berms w idth reqd 1:2.5 no 2 berms 0 0 10 20 30 40 50 slope w idth

If the stereographic projection analysis indicates that there remains a risk of instability in slopes of 1v:1h then consideration will have to be given at detailed design to stabilisation techniques such as:

• Rock anchors/bolts

• Dentition;

• Rock anchors

• Buttressing

• Rock fall catch fencing

8.2.2 Embankment stability

Slopes

The stability of embankment slopes has been assessed in a similar manner to cutting slopes with a general baseline safe angle of slope of 1v:2.5h. Again this assumes that ground water is drawn down to at least one metre below surface.

Where the substrate is very soft or where the ground is side-long then 1v:3h slopes have generally been used because of the risk of edge failures and the impact of high water tables respectively. Again site specific assessments have

been carried out where conditions do not fit the norm. These are described in the individual chapters.

Unless otherwise specified, where analyses have been carried out, and where short term, undrained stability of Class 2 fill embankments is being considered, the fill has been given an undrained shear strength of 50 kPa, which is considered to be a lower bound practical figure for constructing earthworks using remoulded cohesive glacial tills.

Long terms stability of Class 2 fill embankments have been assessed with effective stress parameters of c ' of 0 and φ' of 28 0.

Stability of Class 1 embankments have been assessed with a φ' of 35 0 for the fill.

An HB loading of 20 kN/m 2 has been modelled on the carriageways with a 10 kN/m 2 on the verges.

The required Factor of Safety is 1.3.

The design philosophy for embankments over poor ground conditions are described below.

Materials

In areas of cohesive sub grade embankments should be constructed with a granular starter layer, such as Class 6C, to relieve excess pore water pressure in the underlying material, hence increasing stability and accelerating consolidation. The starter layers would typically be 0.6 m thick.

Starter layers may also be used in areas where band drains are proposed to act as a drainage layer for the drains.

Class 6A material may be more appropriate for use as a starter layer in areas of flood plain which are prone to flooding.

Settlement

Total settlement values for the embankments have been calculated and are presented in each sub section volume. The consolidation settlement has been

determined by the use of m v and c c values derived from oedometer tests and the correlations given in Chapter 6.

Total settlement for clays is generally a combination of immediate settlement plus consolidation settlement. Tomlinson, 2001, indicates that the total settlement can be calculated from oedometer test result using the following relationships:

For stiff over consolidated clays:

Immediate settlement= ρi=0.5 to 0.6 ρoed

Consolidation settlement= ρc=0.5 to 0.4 ρoed

Final settlement = ρoed

Where ρoed = settlement as calculated from oedometer tests.

For soft normally consolidated clays:

Immediate settlement= 0.1 ρoed

Consolidation settlement= ρoed

Final settlement = 1.1 ρoed

Skempton and Bjerrum, 1957 also gives a formula for determining actual consolidation settlement from settlement calculated based on oedometer tests.

ρc=µgρoed

Where µg= a settlement co-efficient which varies with the type of clay.

Tomlinson, 2001 states that all practical purposes it is sufficient to take µ g from the following table.

Table 8-2: Typical µ g Values (After Tomlinson, 2001)

Type of Clay µg

Very sensitive clays (soft alluvial, 1.0 - 1.2 estuarine and marine clays)

Normally consolidated clays 0.7 - 1.0

Overconsolidated clays (e.g. London 0.5 - 0.7 Clay, Weald, Kimmeridge, Oxford and Lias Clays)

Heavily overconsolidated clays (e.g. 0.2 - 0.5 glacial till, Keuper Marl)

Immediate settlement has generally taken place by the time the embankment has been “topped” out. The effect of the immediate settlement is taken account of by placement of additional fill during construction.

It is assumed that any internal settlement due to the weight of the fill is taken out during the construction period.

The assumptions do not take into account any secondary compression from fine grained soils containing a significant proportion of organic soils. The secondary compression value may be significant in areas where there are thick deposits of alluvial material.

Secondary settlement (s s ) can be calculated using the following formula (after Simons, 1974):

s s= H o .c α .log(t f /t o ) Equation 8-1 Where:

Ho= Thickness of compressible material strata following primary consolidation.

cα=Secondary compression index

tf =Time at finish (design life)

to =Time at start of secondary and end of primary consolidation.

Embankments over Poor Ground Conditions

Excavation and Replacement

The alignment crosses a number of areas of peat, both smaller scale areas infilling inter drumlin areas, and also larger raised peat bogs.

If the peat is less than 4 m deep, and in short lengths, up to 5 m deep, excavation and replacement is normally recommended. In this scenario the peat is excavated out and a buried “false” embankment constructed to the original ground level with the new embankment constructed over it. This technique would also apply to at grade sections.

The new embankment would typically be constructed as described above with the buried embankment constructed with side slopes of 1v:2h. Sufficient space should be allowed for a safe angle of slope for temporary excavations into the peat. This would typically be 1v:1h.

Pre earthwork drainage should be installed before excavation and care should be taken to ensure that appropriate excavation techniques are used and that over dig is avoided. Excavations should be carried out using toothless buckets.

A typical section is shown in Figure 8-3.

Figure 8-3: Typical Section for Dig Out and Replace Sites

W=3D Embankment with 1:2.5 side slopes

D Buried Embankment with 1:2 side slopes Soft ground

Solution is viable up to a depth of 4m (5m in very short runs), giving a min Temporary cut width beyond the embankment toe of at 1:1 (may be W=3D backfilled with class 4 fill)

Experience at Cabragh on the A4 between Dungannon and Ballygawley (Aug 2010) has indicated that in many cases, deep inter-drumlin fen deposits consist of less than 3 m of Peat are underlain by normally consolidated clay, silt and sand. The underlying soils, if undisturbed and confined can deliver adequate bearing capacity, subject to managing settlement.

Embankments or at grade sections over deeper areas of peat may be treated in a number of ways. Some examples are given below with more specific information given in the sub section volumes or in the detailed design.

Piled Embankments

For a piled embankment the embankment would be supported on a geotextile reinforced load transfer platform which in turn would be supported by the piles transferring the load to more competent drift deposits at depth or via rock sockets into the rock. Where piled embankments are used, measures must be put in place to protect the piles from future surcharge and/or lateral loading which could result in failure.

Other forms of Ground Improvement under Embankments

Other forms of ground treatment that could be considered are detailed below.

Vibro stone columns could be used in areas where the shear strength of the surrounding material is at least 15 kN/m 2. At lower shear strengths the integrity of the pile will be affected by bulging of the side walls.

Surcharging and staged construction may be considered for low and medium, height embankments. Maximum height of lifts and time for dissipation of excess pore water pressures would be calculated on an individual basis but typical lift heights would be 2-3 m for soft clays. Construction of temporary berms at the base of the slopes and the use of basal geotextile reinforcement may prevent bearing capacity failure on weaker soils and permit higher lifts.

In areas of surcharge it is recommended that the topsoil is not removed prior to construction. This will act as a natural basal reinforcement to the embankment and also aid the trafficking of construction traffic. Level, piezometer and extensometer monitoring will be required to determine when settlement has ceased. Inclinometer monitoring will be required to ensure that no horizontal movement is occurring due to bearing capacity failure caused by loading at a rate in excess of the rate of pore water dissipation.

As stated above, the likelihood of bearing capacity failure can be decreased by the use of temporary side berms which prevent rotational failure of the edge of the main embankment. These will have to be carefully assessed by Finite Element analysis during the detailed design phase to determine their geometry and timescales of placement to ensure that they do not have any adverse impact on the main embankment by down drag.

Light weight fills may be considered where excess settlement is considered to be a problem however sourcing the fill may prove uneconomic. Within the island of Ireland it is understood that that only AES Kilroot Power Station, near Belfast, and Moneypoint Power station, in the Republic, are coal fired power plants (Kilroot is a combined coal/oil plant). It is understood that both power stations produce PFA commercially although in both cases shipment costs may prove excessive.

Other forms of very light weight fill, e.g. Maxit, polystyrene, tyre bales could be considered but these are likely to be very expensive and will also have high shipping costs. It may be that the very light weight fills could be used in the vicinity of settlement sensitive structures with cheaper, less light weight fills, being used further away from the embankments. NIEA have expressed concern about the use of tyre bales and waste regulation. However, pfa and other recycled aggregates should not be subject to waste regulation, provided they are produced in accordance with a recognised protocol.

In areas where the amount of settlement is not an issue but the time for consolidation is, for example in area which is on the critical path for the construction programme, the rate of settlement could be accelerated by the use of band drains or wick drains. These effectively decrease drainage lengths and hence increase the rate of dissipation of excess pore water pressure.

Low embankments, reinforced with a basal grid, may be considered in areas of flood plains. These will aid the movement of construction traffic without causing heavy rutting.

Other forms of improvement may be used. If appropriate these will be discussed in the individual sub sections.

Flood Protection for Embankments

In areas prone to flooding embankments should be protected from scour by placing Class 6A or similar on the embankment slopes which are exposed to the flood waters. This material should be placed to a height of at least 0.5 m above maximum predicted flood levels.

8.2.3 Re-use of Materials

Re-usability has been reviewed by assessing the properties of material likely to be excavated as part of the works against the requirements given in Table 6/1 of the Highways Agency Specification for Highway Works.

For the cohesive material in particular the undrained shear strength and the moisture content of the material is considered critical.

If the undrained shear strength is too low severe rutting and deformation may occur when fill is being placed. A shear strength of 30-50 kN/m 2 (Ref Highways Agency, 1991) is therefore typically used as lower bound strength for re-use.

In addition, for most types of clay fill, under compaction may occur if shear strengths are too high. HA44/91 gives a typical upper bound figure of 150 to 200 kN/m 2. Class 2C, Stony Cohesive Material, however, does not have an upper bound figure as the clast content of the material aids the breakdown of large blocks under compaction. It is likely that the majority of the cohesive glacial till that will be excavated as part of the works will fall into this category.

The re-use potential on the scheme has been analysed by review of natural moisture contents (nmc), optimum moisture contents (omc) from compaction tests, undrained shear strength, moisture condition values (MCVs) and Californian Bearing Ratio (CBR) tests.

These results have been reviewed as relationship packages to determine an overall re-use % for each section. Although individual analyses varied from section to section a typical analysis package included nmc & MCV vs. depth,

nmc vs. CBR, NMC vs. dry density, nmc vs c u , and cu vs. dry density A typical sequence would be to determine the acceptable range of nmc that correlated 2 with a c u of 50 - 150 kN/m , the equivalent dry density that correlates with the

acceptable c u range plus the moisture contents that correspond to 95% of maximum dry density and the 10% air voids line. The min and max moisture contents so obtained could then be plotted onto a nmc vs MCV graph to determine an acceptable range of MCVs. At this stage care was taken to ensure that the maximum and minimum values determined are realistic, for example the lower bound MCV value should be around 7 and erroneously low MCVs were checked to ensure that there were no data errors.

The recorded nmc and MCV values were then plotted as frequency curves and the % of acceptable material determined from the nmc and MCV range determined from the relationship testing.

As a guide any soil with a moisture content leading to a CBR <2%, a c u of <50 kN/m 2, a nmc > optimum moisture content +2%, or a soil with a MCV<7 is probably too wet for reuse for general earthworks fill. It may however, be suitable as Class 4 landscape fill.

Lime improvement and lime stabilisation testing is to be carried out during the supplementary ground investigation in areas of wetter ground to determine whether it is economically feasible or not to improve the percentage recovery of material to be reused elsewhere on site.

Rippability of Rock

In areas of rock cutting an assessment has been of the diggability of the rock to determine whether the rock can be excavated out with plant or whether blasting will be required.

This has been carried out using the Petitifer & Fookes 1994 method, which relates, UCS/Point load values and discontinuity spacing, as shown in Figure 8-5.

An additional method used is that given in Trenter, 2001 which includes a diggability index ranking (Figure 8-5 & Table 8-3) which is used as a basis for a Diggability Classification for Excavators, as shown in Table 8-4. Using this index a suggested type of excavator can be determined.

Figure 8-4: Excavability of Rock (after Petitifer and Fookes, 1994 and Harber et al, 2000)

Point Load Index 0.1 0.3 1.0 3.010.0 30.0 6.0 6.0 216 Blasting or Hydraulic Breaking Very Very Large

2.0 2.0 8 Blasting Required

1.0 1.0 Large 1.0 E x tr em 0.2 0.6 e 0.6 V ly e H ry a H rd a R rd ip

Medium H R pi a ip n r p g d i R n

g Assumes ( l=b=w) ip 0.2 p 0.2 0.08 in g E - - Fracture Spacing Fracture Index (m) a sy Hard Digging R ip

0.1 p 0.1 Small in g

0.06 0.06 0.002

Easy Digging Very Small Equivalent Block (m3) Size 0.02 0.02 2 6 20 60 200 600 Approx. UCS (MPa)

Weak Mod. Weak Mod. Strong Strong V.Strong Extremely Strong Strength

Figure 8-5: Diggability Chart (after Trenter, 2001)

Table 8-3: Diggability Index rating (after Trenter, 2001)

Table 8-4: Excavation Diggability Classification (after Trenter, 2001)

8.3 Highway Structures

Recommendations will be given in the sub section reports for options at the individual sites.

Settlement has been calculated as described above.

8.4 Strengthened Earthworks

These will be discussed on a case by case basis in the sub section volumes although the general philosophy for ground improvement is discussed in Chapter 8.2.2

8.5 Drainage

To avoid softening of formation and potential instability pre-earthworks drainage is required at the following types of locations:

• Filter drains on both sides of the carriageway to drain the capping/sub- base and maintain a dry formation and hence increase CBR values.

• A filter drain at the toe of all cuttings to maintain a minimum 1 m depth of groundwater at the toe.

• Ditches at the toe of embankments to control run off and increase the stability of the embankment. The ditches should be placed at least 2 m away from the embankment toe in order to avoid an apparent increase in the height of the embankment height.

• Crest drainage should be installed in all cutting locations where land slopes towards the cutting. Normally this would be a V ditch but if there is insufficient space a filter drain should be installed (Ref. BS6031).

• Existing field drains which are likely to be cut by the construction should be intercepted by collector drains.

In certain circumstances drainage may be required during construction, such as temporary ditches in cuttings to improve the stability of side slopes in silts and sands below the water table and also to maximise the re-use potential of the more silty tills in times of adverse weather.

The glacial tills frequently contain discontinuous water bearing, more granular horizons. If left untreated water issuing from these horizons can cause localised failures which quickly grow in magnitude by “back sapping” failures where wash outs cause lack of support for overlying materials. Allowance should therefore be made for the installation of herringbone, counterforts or filtered blanket drains on cutting slopes during cutting construction. These drains should feed into the cutting toe drains.

On embankments it is recommended that surface channels are used to take run off from carriageways to toe ditches to avoid any issues with stability of the embankments. If over the edge drainage is used the effect of wetting the embankment material should be considered in the design.

8.6 Pavement Design, Subgrade and Capping

For preliminary design purposes pavement foundation design has been carried out in accordance with IAN73/06 Design Approach 1 - Restricted Foundation Design (RFD). This approach is conservative, however and is recommended that the detail design uses Design Approach 2 – Performance Foundation Design. It should be noted that Performance Foundation Designs will require a Departure. Design Approach 2 will not be discussed further in this report.

IAN 73/06 defines four foundation classes based on the Foundation Surface Modulus Value 1.

• Class 1 ≥ 50 MPa

• Class 2 ≥ 100 MPa

• Class 3 ≥ 200 MPa

• Class 4 ≥ 400 MPa

The RFD can be used for Foundation Classes 1, 2 and 3. Foundation Class 1 is not permitted for Trunk Roads therefore only Classes 2 and 3 are considered for this report.

The RFD method requires the estimation of the Subgrade Modulus 2 which is determined using the lowest value of the long term and short term CBR.

1 Foundation Surface Modulus: A measure of the ratio of applied stress to induced strain (Stiffness Modulus) based on the application of a known load at the top of the foundation; it is a composite value with contributions from all underlying strata.

2 Subgrade Modulus: an estimated value of Stiffness Modulus based on subgrade CBR and used for foundation design

CBR values determined using laboratory tests are generally short term CBR values. Long term, equilibrium values for cohesive materials have been determined using Plasticity Indices. Table 5.1 of IAN 73/06 tabulates estimated CBR values from PI data and grading results however it is recommended that the table from the original issue of IAN 73/06 is used to determine CBR values (reproduced as Table 6-7) as this brings in variations in water table and construction conditions. For preliminary design purposes average construction conditions have been assessed with variations in water table altered to suit the particular site conditions. A thick construction 3 has been assumed for preliminary design.

In order to keep the water table at the levels assumed in IAN 73/06 it is recommended that for areas where the road is at grade, or in cut, drains are installed from a level above the phreatic surface as excavation proceeds, to allow for some draw down during construction. In addition the use of a coarse capping, possibly increased in thickness during construction, should be considered. Capping will assist in traffickabiility during the construction phase and will provide lateral drainage from the subgrade. Due to the low permeability of the more cohesive glacial tills it is not likely that drawdown will have fully occurred during construction. Construction thicknesses should be designed assuming drawdown to subgrade level only in the short term.

It is assumed that embankments constructed out of Class 2 material will have good quality material in the upper 1.0m and that a design CBR value of 5% can be used. It is recommended that 210mm of capping is used to improve the CBR value to 15%.

Where embankments are constructed out of Class 1 material a design CBR value of 15% is recommended, provided the upper 1m does not contain any argillaceous material that is susceptible to breakdown under loading or weathering.

Due to the silty nature of the glacial tills road construction thickness should be at least 450mm thick to avoid heave due to the frost susceptibility of the construction.

Where weathered granular rock is present at sub grade depth a CBR of at least 15% can be assumed.

3 Thick construction is a depth to subgrade of 1200 mm.

Where unweathered strong rock is present a CBR of at least 30% can be assumed. Sub base can be omitted in this instance, providing a regulating sand layer of at least 150 mm is used to even out hard spots, and to ensure that the pavement construction thickness is uniform.

Verge side drainage is required to ensure that any argillaceous rock does not weather in the long term to a point where assumptions with respect to the design CBR are no longer valid.

8.7 Contaminated Land

A discussion about any contaminated land is contained in Volume 9 of this report.

8.8 Ground Treatment Including Treatment of any Underground Voids etc.

8.8.1 Soft Spots

In at grade sections, where soft spots are encountered (CBR<2.5% or c u <50 kPa), these should be excavated out and replaced by Class 1, 2 or Class 6 material. If the excavation of the soft material is below water the replacement material should be Class 6A (Selected Well Graded: Below Water).

8.8.2 Water Courses

If any water courses have to be diverted as part of the works the abandoned channels should be treated as per the soft spots, with the channel and any associated soft material excavated out and replaced with Class 1, 2 or Class 6 material. Low permeability clay should be used to “plug” the upstream side of the channel.

8.9 Specification Appendices

Not included in outline design.

8.10 Instrumentation and Monitoring

General requirements are discussed for the individual earthworks chapters with specific requirements discussed at detailed design stage.

Principal Symbols

Table 8-5: Principal Symbols Symbols Name Units

CBR Californian Bearing Ratio %

2 ch Co-efficient of Horizontal Consolidation m /yr

2 cv Co-efficient of Vertical Consolidation m /yr

Cc Compression Index

Cs/ C c Swelling/re-compression Index

Cα Coefficient of secondary compression

cu Undrained (total) shear strength parameter kPa or kN/m 2

c’ Drained (effective stress) shear strength kPa or parameter kN/m 2

D Disturbance Factor

e0 Initial Void Ratio

e1 Void Ratio after an incremental loading

E Young’s Modulus MPa

Eu Undrained (Short Term) Young’s Modulus MPa

E’ Drained (Equilibrium) Young’s Modulus MPa

Erm Rock Mass Modulus MPa

Ei Intact Rock Modulus MPa

Symbols Name Units

Gs Specific Gravity

Is Point Load Index

Ip Plasticity index %

j Rock Mass Factor

kh Co-efficient of Horizontal Permeability m/s

kv Co-efficient of Vertical Permeability m/s

JRC Joint Roughness Coefficient

JCS Uniaxial Compressive Strength of Rock in Joint MPa Wall

LI Liquidity Index %

2 mv Coefficient of volume compressibility m /MN

N100 Penetration resistance for a Super Dynamic probe Heavy over 100mm range

N Standard Penetration Resistance

N’ k Effective Cone Factor

M Penetration Resistance for Mackintosh Probes over 100mm

Mr Modular Ratio

qc CPT cone end resistance MPa

w Moisture content %

Symbols Name Units

3 γw Unit weight of water kN/m

σ'cf Uniaxial Compressive Strength (generally rock) MPa or MN/m 2

σ'v Effective Vertical Stress (pressure) kPa or kN/m 2

σ'c Pre consolidation pressure kPa or kN/m 2

φ' Effective angle of shearing resistance degrees

φ'max Maximum (peak) angle of shearing resistance degrees

φ'crit Critical state angle of shearing resistance degrees

φ'mar Residual angle of shearing resistance degrees

φb Sliding resistance on discontinuities degrees

ρi Immediate settlement mm

ρo Settlement calculated from oedometer mm

2 Τr Shear resistance along discontinuity kN/m

µg Settlement coefficient

References

6.1. Barnes, G, 2000, Soil Mechanics Principles and Practice, Macmillan

6.2. Barton, N.R. 1973. Review of a New Shear Strength Criterion for Rock Joints. Eng. Geol. 7, 287-332.

6.3. Barton, N.R. and Choubey, V., 1977, The Shear Strength of Rock Joints in Theory and Practice, Rock Mechanics.

6.4. Bergado, D.T., Chai, J.C., Alfaro, M.C. & Balsubramanium, A.S, 1994: Improvement Techniques of Soft Ground in Subsiding and Lowland Environment

6.5. BS6031, 1981, Code of Practice for Earthworks

6.6. BS8002, 1994, Code of Practice for Earth Retaining Structures

6.7. Brouwer, J.M.M, 2007, www.conepenetration.com/online-book , Lankelma

6.8. Black, W.P.M. and Lister, N.W., 1979, The Strength of Clay Fill Subgrades, its Prediction in Relation to Road Performance, Report LR 889, Transport and Road Research Laboratory

6.9. Card, G.B., Roche, D.P. & Herbert, S.M, 1990, Applications of Continuous Dynamic Probing in Ground Investigation, Geological Society, London, Engineering Geology Special Publications v. 6;

6.10. Carter, M. & Bentley, S.P., 1991, Correlations of Soil Properties, Pentech Press

6.11. Cearns, P. J. & McKenzie, A., 1988, Application of Dynamic Cone Penetrometer Testing in East Anglia, Geotechnology Conference on Penetration Testing in the UK. Paper 12.

6.12. Chandler, R. J, 1988, The In Situ Measurement of the Undrained Shear Strength of Clays Using the Field Vane, STP 1014, Vane Shear Strength Testing in Soils: Field and Laboratory Studies, ASTM

6.13. Craig, R. F., 2004, Soil Mechanics 7 th , SPON Limited

6.14. EN ISO 22476-2, 2005, Geotechnical Investigation and Testing -- Field testing - - Part 2: Dynamic probing

6.15. EN ISO 22476-3, 2005, Geotechnical Investigation and Testing -- Field testing - - Part 3: Standard penetration test

6.16. European Committee for Standardization, 1997: EN 1997, Eurocode 7 – Geotechnical Design

6.17. Farmer, I., 1983, Engineering Behaviour of Rocks, 2 nd Edition, Chapman and Hall Limited

6.18. Fakher, A., Khodaparast, M. & Jones, CJ.F.P., 2006, The use of the Mackintosh Probe for site investigation in soft soils, Quarterly Journal of Engineering Geology v39.

6.19. Gibson, R.E., 1953, Experimental Determination of the True Cohesion and True Angle of Internal Friction in Clays, Proceedings of 3 rd International Conference on Soil Mechanics and Foundation Engineering

6.20. Hobbs, N.B., 1986, Mire Morphology and the Properties and Behaviour of Some British and Foreign Peats, Quarterly Journal of Engineering Geology

6.21. IAN 73/06 Revision 1, 2009, Design Guidance for Road Pavement Foundations (Draft HD25), Highways Agency

6.22. Ladd, C.C., Foote, R., Ishihara, K., Schlosser, F., and Poulus, H.G., 1977, Stress Deformation and Strength Characteristics, Proceedings Ninth International Conference on Soil Mechanics and Foundation Engineering

6.23. Mouchel, 2010, Mouchel Internal Memo, Guidance On Selection Of Characteristic Values Of Geotechnical Parameters;

6.24. Peck, R.B., Hanson, W.E. and Thorburn, T.H., 1974, Foundation Engineering, 2nd edition, John Wiley and Sons

6.25. Schofield, A.N. and Wroth, C.P. 1978, The correlation of index properties with some basic properties of soils, Canadian Geotechnical Journal, 15(2), May, pp.137-145

6.26. Skempton, A.W., and Bjerrum, L., 1957, A Contribution to the Settlement of Foundations on Clay, Geotechnique

6.27. Stroud, M.A. and Butler, F.G., 1975, The Standard Penetration Test and the Engineering Properties of Glacial Materials, Proc. Symp. Engineering Properties of Glacial Materials, Midlands Soil Mechanics and Foundation Society

6.28. Spagnoli, G., 2008, An Empirical Correlation Between Different Dynamic Penetrometers; Electronic Journal of Geotechnical Engineering

6.29. Terzaghi, K and Peck, R.B, 1967, Soil Mechanics in Engineering Practice, 2 nd edition, John Wiley and Sons

6.30. Tomlinson, M.J., 2001, Foundation Design and Construction, 7 th Edition, Pearson

6.31. Wroth, C.P. and Wood, D.M., 1978, The Correlation of Index Properties with some Basic Engineering Properties of the Soils, Canadian Geotechnical Journal

8.1. Bieniawski, Z.T. (1976) Rock Mass Classifications in Rock Engineering, Proc. Symp. Expl. Rock Eng., Johannesburg, Balkema, Cape Town, Vol. 1 pp. 97- 106

8.2. Pettifer, G. S. & Fookes, P. G., 1994, A Revision of the Graphical Method for Assessing the Excavatability of rock.. Quarterly Journal of Engineering Geology.

8.3. Simons, N.A., Review paper: Normally consolidated and lightly over consolidated cohesive materials, in Proceedings of the Conference on Settlements of Structures, Pentech Press, Cambridge, 1974, pp. 500-530

8.4. Trenter, N.A., 2001, Earthworks: a Guide, Thomas Telford

Appendix A – Geotechnical Certificate

Geotechnical Certificate

Scheme Title – A5 Western Transport Corridor Certification Ref GW163

(*- Delete as appropriate) Certificate Seq. No 4C

Form of Certificate to be used by the Designer for certifying the design of geotechnical works

1. We certify that the Reports*, Design Data*, Drawings* or Documents * for the Geotechnical Activities listed below have been prepared by us with reasonable professional skill, care and diligence, and that in our opinion: i. constitute a fit for purpose and economic design for the project

ii. solutions to all the reasonably foreseeable geotechnical risks have been incorporated

iii. the work intended is accurately represented and conforms to the Employer's */Client's* requirements

iv. with the exception of any item listed below or appended overleaf, the documentation has been prepared in accordance with the relevant standards from the Design Manual for Roads and Bridges and the Manual of Contract Documents for Highway Works.

*where the certificate is accompanying revision to design data already certified the following statement shall also be included*

v. *The design elements covered by this certificate are not detrimental to the design elements previously certified and not amended by this certificate*

2. List of Reports, Design Data, Drawings or Documents

Document no. 718736/0600/R/008 Section 2, South of Strabane to South of Omagh, Ground Investigation Report – Volume 1 Introduction and General Principles

3. Departures from Standards

None

List of any departures from relevant standards (if none write “none”)

4. Incorporation of Geotechnical Data Into Construction Details

Not applicable

Signed: ………………………….

Designer (Designers Geotechnical Advisor)

Name: David Towell………………………….

Date: 21 September 2010…………………………

On behalf of Mouchel

This Certificate is:

(a) received* (see note)

(b) received with comments as follows:* (see note)

Signed: ………………………….

Overseeing Organisation Geotechnical Advisor

Name: ………………………….

Date: ………………………….

Note:

'Received' = Submission accompanying certificate is accepted.

'Received with comments' = Submission accompanying certificate generally acceptable but require minor amendment which can be addressed in subsequent revisions.

'Returned marked comments' = Submission accompanying certificate unacceptable and should be revised and resubmitted.

Appendix B – Guidance on Navigating the GIS Data

Guide to Navigating the GIS Model

Introduction

To aid with the management of the large volume of information gathered and assessment of parameters, it was decided to present the information and drawings electronically within the Arc Reader (GIS) Model. Arc Reader not only presents the information spatially but also provides additional supplementary information about the features shown, either by hovering over and/or clicking on the symbology for the particular geo-environmental feature. General advice on how to use Arc Reader is contained in this report.

Getting Started

Opening the Arc Reader GIS Model

Access the hard drive containing the model in “My Computer”

Within the hard drive, double click on the icon showing the GIS Model, labelled A5WTC_Geotechnical_ArcReader_GIS_Model:

Using the Arc Reader GIS Model

Upon start-up, a window showing the proposed scheme layout and study area will appear with the toolbar and the navigation pane from which the appropriate drawings or layers of interest can be selected for viewing, as illustrated below:

Tool bar

Navigation pane

Drawings

The model can be freely navigated between layers and combinations of layers or alternatively, set combinations have been set up in the navigation toolbar, corresponding to standard drawing information views.

To view a drawing, select the particular drawing from the navigation pane which will refresh the screen with the appropriate layers and then use the zoom tools to zoom into the geographic region of interest.

Schedule of Drawings Reference in GIR

Drawing Number Drawing Title Description of Drawing

796036-0600-D-00061B A5 Western Transport Map illustrating the extents of the A5 Western Transport Corridor Scheme and including the engineering study area and preferred Corridor Scheme Split corridor. 796036-0600-D-00062B Historical Exploratory & Illustration of locations for all historical ground information gathered as part of the desk study. Borehole logs associated with the Preliminary GI exploratory hole locations are hyperlinked within this drawing. Locations 796036-0600-D-00063B Drive through Survey Drawing providing information gathered during a Drive Over Survey in March 2008 including brief field notes within the callouts and Notes & Photographs hyperlinks to photographs. 796036-0600-D-00064B Walkover Survey Drawing providing information on the key geological & geomorphologic features gathered during a Walkover Survey in April 2008 Reports and including short field notes and hyperlinks to photographs. Also included within this drawing are hyperlinks to the Walkover Reports Photographs produced by Mouchel. 796036-0600-D-00065B Quarry and Landfill Drawing providing information gathered during a Quarry and Landfill Survey in August 2008 to establish the status of the many Survey quarries and landfills identified within the scheme, including short field notes and hyperlinks to photographs. 796036-0600-D-00066B Peat Survey Drawing providing information gathered during a Peat Survey in July 2008 identifying the stability of the peat bogs, including short field notes and hyperlinks to photographs. 796036-0600-D-00068B 3-D interpretation of the This drawing illustrates the main geomorphologic features using a 3-D interpretation of the terrain which shades the relief in 100m terrain intervals. 796036-0600-D-00069B Steepness of the terrain This drawing conveys the steepness of the terrain with colour coding of the slope gradients. 796036-0600-D-00077B Bedrock Geology This drawing can be viewed in conjunction with Section 4.6.1 of the PSS report to identify the underlying solid geology for the scheme. Section 4.6.1 includes the full names for the abbreviations of the rock formations shown on the drawing. 796036-0600-D-00078B Superficial Geology This drawing can be viewed in conjunction with Section 4.6.2 of the PSS report to identify the drift geology for the scheme. 796036-0600-D-00079B Hydrogeological Map The hydrogeological map indicates the resource potential for the aquifers underlying the study area.

Drawing Number Drawing Title Description of Drawing

796036-0600-D-00080B Groundwater The groundwater vulnerability map indicates the significance of pollution incidents occurring to the underlying aquifers. Vulnerability Map 796036-0600-D-00095 Main GI Locations This drawing displays the locations of the main ground investigation sites for all sections, displaying coloured symbols to denote each type of investigation and phase of work. 796036-0600-D-00096 Extent of each GIR Geographical extent covered by each of the GIR volumes volume 796036-0600-D-00097 Earthwork split Drawing provided to display the labelling and details of the earthworks along the route alignment. 796036-0600-D-00098 Structures locations and This drawing is provided to display the locations of all structures along the alignment and hyperlinks to display detailed summaries of datasheet hyperlinks each. (incl culverts, retaining structures and attenuation ponds) 796036-0600-D-00099 Proposed engineering Geotechnical mitigation extents for soft ground recommendations

Tool Bar

The tool bar is located at the top of the screen. Hovering the cursor over each tool allows a preview of the tool function. The functionality of these tools are described below in more detail.

Measure Navigation pane Scale Find

Pan Identify Hyperlinks Zoom Go to X,Y

Transparency Highlighter

PAN

The pan tool can be used to move around the map. When activated, click and hold to drag the map in the direction required.

ZOOM

To zoom in and out of the map use the icons below accordingly. Click and hold to drag a zoom box over the required area.

A5 WTC - Section 2 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

To zoom to a predetermined scale use the fixed zoom tool

The dynamic zoom tool is used by dragging the cursor up and down to zoom in and out respectively.

Interpreting Features

The identity tool is used to retrieve information about a feature

The measure tool is used to calculate the distance between two points.

The hyperlink tool is used to open documents / photographs linked to a feature

A5 WTC - Section 2 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

Layer Navigation

The menu on the left of the screen allows navigation between the layers. The layers can be expanded to reveal the categories and details within:

Main Layer