Section 3, South of Omagh - Aughnacloy

Ground Investigation Report – Volume 1 Introduction and General Principles

November 2010

Document Ref No 718736/R/0600/008 Volume 1 of 13

For Department for Regional Development

Roads Service Ref GW163

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

T 028 90424117 F 028 90427039 A5 Western Transport Corridor - Section 3 Ground Investigation1.1.1.4 Report – Volume 1 Introduction and Job_Name4 General Principles

Document Control Sheet

Project Title A5 Western Transport Corridor

Report Title Section 3 - Ground Investigation Report – Volume 1 Introduction and General Principles

Report Reference 718736/R/0600/008

Version A

Issue Date November 2010

Record of Issue

Version Status Author & Date Checked & Date Authorised & Date

A 1st Issue S MCusker 08/10 M Jackson 08/10 D Towell 02/11

M Rea 08/10 A Wheeler 08/10

Distribution

Organisation Contact Format Copies

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

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

Jacobs Engineering UK Limited L Davison – Technical PDF 1 Director (on behalf of RS HQ)

Mouchel D Parody –Manager PDF 1

Table 1-1: Geotechnical Reports – List of Volumes GIR Report Number Title Start End Volume CH CH

1 718736-0600-R-008 Introduction and General 61480 93130 Volume 01 of 11 Principles

2 718736-0600-R-008 Findings of the Investigation, Section 61480 64350 Volume 02 of 11 3A: South of Omagh – Drumconnelly Road

3 718736-0600-R-008 Findings of the Investigation, Section 64350 68930 Volume 03 of 11 3B: Drumconnelly Road - Moylagh

4 718736-0600-R-008 Findings of the Investigation, Section 68930 73650 Volume 04 of 11 3C: South of Moylagh- Newtownsaville

5 718736-0600-R-008 Findings of the Investigation, Section 73650 80035 Volume 05 of 11 3D: Newtownsaville - Errigal

6 718736-0600-R-008 Findings of the Investigation, Section 80035 83090 Volume 06 of 11 3E: Errigal – North of Ballygawley Junction 7 718736-0600-R-008 Findings of the Investigation, Section 83090 83900 Volume 07 of 11 3F: Ballygawley Junction

8 718736-0600-R-008 Findings of the Investigation, Section 83900 88575 Volume 08 of 11 3G: South of Ballygawley Junction to Tullyvar

9 718736-0600-R-008 Findings of the Investigation, Section 88575 93130 Volume 09 of 11 3H: Tullyvar - Aughnacloy

10 718736-0600-R-008 Environmental Testing Analysis 61480 93130 Volume 10 of 11

11 718736-0600-R-008 Risk Register 61480 93130 Volume 11 of 11

This Volume (Volume 1) is highlighted in Bold in Table 1-1 above

LIMITATIONS

This report is presented to the DRD Roads Service in respect of A5 Western Transport Corridor (WTC) – Section 3 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 DRD 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...... 8 2 Introduction...... 10 2.1 Description of the Project...... 10 2.2 Scope and Objective of the Report ...... 16 2.3 Geotechnical Category of Project ...... 18 2.4 Other Relevant Information...... 18 3 Existing Information...... 19 3.1 Sources of Information...... 19 3.2 Previous Ground Investigations ...... 22 3.3 Other Relevant Information...... 22 4 Field and Laboratory Studies...... 23 4.1 Walkover Survey ...... 23 4.2 Geomorphological/Geological Mapping ...... 23 4.3 Ground Investigation ...... 23 4.4 Drainage Studies...... 28 4.5 Geophysical Survey...... 28 4.6 Pile Tests...... 29 4.7 Other Field Work ...... 29 4.8 Laboratory Investigation ...... 29 5 Ground Summary ...... 32 5.1 Geography...... 32 5.2 Topography ...... 32 5.3 Historical Development...... 33 5.4 Man-made Features – Mining and Quarrying...... 34 5.5 Hydrology ...... 34 5.6 Geology...... 34 5.7 Hydrogeology ...... 40 6 Ground Conditions and Material Properties...... 43 6.1 Introduction...... 43 7 Geotechnical Risk...... 67 8 Basic Design Philosophy and Methodology...... 68 8.1 Introduction...... 68 8.2 Earthworks ...... 69 8.3 Highway Structures ...... 84 8.4 Strengthened Earthworks ...... 85 8.5 Drainage...... 85 8.6 Pavement Design, Subgrade and Capping...... 86 8.7 Contaminated Land ...... 88 8.8 Ground Treatment Including Treatment of any Underground Voids etc. ... 88 8.9 Specification Appendices...... 88 8.10 Instrumentation and Monitoring ...... 88 Principal Symbols ...... 89 References...... 92

Tables

Table 1-1: Geotechnical Reports – List of Volumes ...... iii

Table 2-1: Section Limits...... 12

Table 2-2: Parties to the Project...... 15

Table 2-3: Report Volumes...... 16

Table 3-3-1: Sources of Information ...... 19

Table 3-3-2 Utilities ...... 22

Table 4-1: Drawings showing locations of field survey data ...... 23

Table 4-2: Summary of GI Works ...... 25

Table 4-3: Summary of Geotechnical Laboratory Testing...... 30

Table 6-1: Range of Field values of k h / k v ratio (after Bergado et al 1994) ...... 45

Table 6-2: Typical permeability values for Soils (Carter and Bentley, 1991).....46

Table 6-3: φφφ' for Siliceous Sands and Gravels ...... 48

Table 6-4: Relationship between Cone Resistance, Phi and Young’s Modulus (Ref. Eurocode 7) ...... 49

Table 6-5: Critical Angle of Internal Friction from Plasticity Index (BS 8002)..53

Table 6-6: Overconsolidation Ratios (After Barnes, 2000) ...... 60

Table 6-7: Equilibrium Subgrade CBR Estimation...... 61

Table 6-8: Basic friction Angle on Discontinuities (after Barton and Choubey, 1977) ...... 63

Table 6-9: Modular Ratios (After Hobb’s 1974) ...... 66

Table 6-10: Rock Mass Factors (After Hobbs, 1974)...... 66

Figures

Figure 2-1 Regional Context Plan ...... 10

Figure 6-1: c h values derived from t 50 values (after Robertson et al 1992)...... 44

Figure 6-2: Relationship Between N value, Phi and Relative Density (after Peck et al, 1967) ...... 47

Figure 6-3: Relationships between angles of internal friction and insitu tests 49

Figure 6-4: CPT N Value Correlation...... 50

Figure 6-5: Terzaghi and Peck method for Calculating Allowable Bearing Pressure ...... 51

Figure 6-6: Angle of Internal Friction Determined from Plasticity Index...... 53

Figure 6-7: Variation of f1 with Plasticity Index (after Tomlinson, 2001)...... 54

Figure 6-8: Variation of f2 with Plasticity Index (after Tomlinson, 2001)...... 56

Figure 6-9: Correlation between sensitivity and liquidity index (after Cater and Bentley, 1991)...... 57

Figure 6-10: Joint Roughness Co-efficient (After Barton & Choubey, 1977) ....64

Appendices

Appendix A Geotechnical Certificate Appendix B Guide to Navigating the GIS Model Appendix C Ground Investigation Factual Report

1 Executive Summary

The objective of the A5 Western Transport Corridor (A5 WTC) proposed 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 north west of the island of Ireland.

For logistical reasons the proposed 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 the ground investigation carried out in Section 3 between September 2009 and April 2010. Sections 1 and 2 of the proposed scheme are reported separately.

The proposed scheme south of Omagh follows an alignment west of the existing road passing east of Seskinore and Newtownsaville and to the west of Garvaghy Big Hill before descending the Brougher Ridge between Tycanny Hill and Birneys Hill near Errigal. As the proposed scheme enters the Clogher Valley, it heads east and crosses the A4 south west of Ballygawley. South of Ballygawley it follows a broad sweep to the east of Aughnacloy before joining the existing A5 at Moy Bridge, immediately north of the border with the Republic of Ireland.. Section 3 is approximately 31.5km long.

The ground conditions in Section 3 split easily into three zones defined by the underlying geology. The boundaries follow two prominent SW-NE trending geological faults. The northern and southern blocks are characterised by relatively low lying drumlin landscape, with the Slievemore Ridge forming a block of high ground between them.

The superficial geology of the area is dominated by glacial deposits comprising glacial till and glacio-fluvial sand and gravel. More recent alluvial and organic deposits occur in isolated pockets throughout the proposed scheme overlying the glacial deposits. The underlying geology is underlain by Devonian and Carboniferous age rocks that predominantly consist of sandstone, but with some mudstone and (in the south) limestone.

In June 2009, Mouchel designed and supervised a ground investigation of the proposed alignment at the time. The fieldwork took place between September 2009 and March 2010 and comprised 180 cable percussion boreholes, 165 of which also had rotary coring, 209 trial pits, 19 window samples, 38 dynamic probes, 24 Mackintosh probes and 8 CPT’s. The purpose of the investigation was to gain an understanding of the ground conditions along the proposed

alignment, to delineate areas of soft ground and to provide geotechnical parameters for design of the earthworks, structure foundations and road pavement.

Due to the length of the proposed scheme, the Ground Investigation Report (GIR) is split into 11 sub volumes, this being Volume 1. This volume describes the purpose of the proposed scheme, a summary of the ground investigation and the ground conditions encountered plus a summary of the design principles which will be used in subsequent volumes. Volumes 2 to 9 of the GIR, describes in detail the ground conditions and the material properties of the 8 sub sections. These have been divided on the basis of topography, proposed works and geology. Volume 10 describes the results of the contamination testing carried out on soil samples taken in the Section and Volume 11 contains the geotechnical risk register.

2 Introduction

2.1 Description of the Project

2.1.1 Regional Context

The A5 Western Key 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 in Figure 2-1.

Figure 2-1 Regional Context Plan

The proposed 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 a combination of at grade separated junctions.

2.1.2 Proposed 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 north west of the island of Ireland.

The Roads Service objectives are to deliver the preferred scheme in accordance with the current DMRB standards and in accordance with current 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 is being developed between all interested parties to optimise the delivery of the project.

2.1.3 Geotechnical Objectives

The geotechnical objectives of the proposed 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 proposed scheme and the associated land to be vested by the Department. Factors which will be considered include the design, construction method, safety, cost and programme of construction and the geo-environmental impacts of the proposed 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 Proposed Scheme Section

For logistical reasons, the proposed scheme has been divided into three 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 3.

2.1.5 Development of the Proposed 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 proposed 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 April 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 3 of the proposed scheme.

2.1.6 Description of the Preferred Scheme in Section 3

The proposed scheme is described below from north to south, extending from north west of the Seskinore Road (CH 61480) south of Omagh, to Moy Bridge (CH 93130) at the border with the Republic of Ireland just south of Aughnacloy. The proposed scheme extends west of the existing A5 for the most part, except for the most southerly section where the proposed scheme forms a loop diverging to the east of Aughnacloy (CH88400).

• South of the Seskinore Road junction (CH 62070), the proposed scheme crosses an area of peat bog on embankment to CH 64000, crossing under the Tattykeel Road in the vicinity of Doogary.

• The proposed scheme alternates through areas of cutting and embankment passing under Drumconnelly Road (CH 64400), Rarone Road (CH66900) and over Tullyrush Road (CH 66000) crossing Moylagh Road at CH 68800 where a grade separated junction will be provided.

• The proposed scheme continues south of Moylagh junction through a large cutting (up to 23m depth) for 600m before progressing predominantly on embankment to CH72600, passing over the Greenmount Road (CH 71100) and Routing Burn River (CH 71650). ,

• Further south the proposed scheme extends largely on embankment passing over the Springhill Road (Ch 73770) and skirting the eastern edge of a peat bog south of Newtownsaville.

• The proposed scheme continues in a south easterly direction bisecting through the east-west aligned Slievemore ridge creating substantial cuttings as it passes through west of Tycanny Hill. The proposed scheme crosses over Tullnafoile Road (CH 75850), Rarogen Road (CH 78425), under the Tullycorker (CH 76620) and Glenhoy Road at CH 80200, immediately west of Errigal Church.

• South of the church the proposed scheme passes under the Ballynasaggart Road (CH 81700) before crossing the Annaghilla Road (CH 83400) where there will be an intersection providing links to the A4 and existing A5, crossing the Ballygawley Water twice.

• The proposed scheme then continues along a south easterly orientation from the Ballygawley interchange passing over Tullywinny Road (CH84300), Lisginney Road (CH 86400) and Old Chapel Road (CH 87700) before passing west of the active landfill site at Tullyvar.

• The proposed scheme crosses under the A5 Tullyvar Road (CH 88400), where a limited movement grade separated junction will provide connectivity to the existing A5 and Loughans Road.

• The proposed scheme follows a loop to the east of Aughnacloy passing under Carnteel Road (CH 90300) and over Renaghy Road at CH 91900, before tying in with the existing A5, approximately 100m north of Moy Bridge.

There are no significant structures on the proposed scheme, but key points include:-

• Grade separated junction at the Seskinore Road (CH 62070)

• A piled structure to cross the peat bog at Doogary (CH 63150 – 64000)

• Grade separated structure at the Junction with Moylagh Road and Augher Point Road (CH 68700)

• Bridge over the Routing Burn

• Bridge over the Ballygawley Water, south of the A4 intersection at CH 83800

• Grade separated junction at Tullyvar Road (CH 88400)

Moy Bridge over the Blackwater River will not be modified as part of the proposed scheme.

Structure locations are shown on drawing 796036-0600-D-00098A.

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, BT79 7AF Drive, Holywood, County Down,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, 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 Graham Farrans JV

Address Unit M, 280 Comber Rd, Lisburn, Ballygowan Rd, Hillsborough, Co BT27 6TA Down, BT26 6HZ

Telephone 028 9263 9647 028 9268 9500

Contact Mr Colm Hurley Mr Paul Scott

[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 proposed scheme were appointed under an Early Contractor Involvement (ECI) framework, in order to obtain their experience and views on most practical and economic construction methods.

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

2.2 Scope and Objective of the Report

This document refers to A5 WTC Section 3, from South of Omagh to Aughnacloy. The report has been split into the following volumes;

Table 2-3: Report Volumes Volume Title

1 Introduction & General Principles

2 Findings of the investigation, Section 3A: South of Omagh - Drumconnelly Road

CH 61480 To 64350,

3 Findings of the investigation, Section 3B: Drumconnelly Road - Moylagh

CH 64350 To 68930,

4 Findings of the investigation, Section 3C: South of Moylagh - Newtownsaville

CH 68930 To 73650,

5 Findings of the investigation, Section 3D: Newtownsaville - Errigal

CH 73650 To 80035,

6 Findings of the investigation, Section 3E: Errigal – North of Ballygawley Junction

CH 80035 To 83090,

7 Findings of the investigation, Section 3F: Ballygawley Junction

CH 83090 To 83900,

8 Findings of the investigation, Section 3G: South of Ballygawley Junction - Tullyvar

CH 83900 To 88575,

9 Findings of the investigation, Section 3H: Tullyvar - Aughnacloy

CH 88575 To 93130,

10 Environmental Testing Analysis

11 Risk Register

Drawing 796036-0600-D-000096A shows the geological area covered by each subsection covered by volumes 2-9.

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

This volume includes the following;

1 – Executive Summary

2 - Introduction

3 – Existing Information

4 – Field and Laboratory Studies.

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 proposed 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. Risks relating to each subsection are detailed in Chapter 7 which, in turn form the basis of the risk register for Section 3.

Chapter 8 will contain outline design recommendations for earthworks and foundations of the sub-section. These recommendations will be developed as part of the detailed design which will take place after the proposed scheme has passed the public inquiry.

Due to the length of the proposed scheme, drawings are provided as navigable layers on a GIS model. Appendix B contains a guide to navigating the model.

2.3 Geotechnical Category of Project

The project has been classified as Category 2 overall, with particular elements classifying as Category 3 in accordance with the principles of HD22/08 (implemented in Northern Ireland by Roads Service standard RSPPG_E_008).

• 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.

The piled embankment across the peat bog at Doogary is currently considered as Category 3. It should be noted, however, that the Geotechnical Classification should be reviewed as the proposed scheme progresses and additional geotechnical issues could be added to this Category 3 list.

2.4 Other Relevant Information

Not Used.

3 Existing Information

A geotechnical Preliminary Sources Study (PSSR) for Section 3 was carried out by Mouchel in June 2009 (Ref: 796036-0600-R-007). 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 3 PSSR and includes any new information received since the publication of the PSSR.

3.1 Sources of Information

The information records pertaining to the proposed 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 proposed 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 Geological Survey of 1:250 000 Geological Map of Solid geology along proposed scheme Northern Ireland Northern Ireland (Solid corridor Edition) (GSNI) 1:250 000 Geological Map of Quaternary deposits along proposed Northern Ireland (Quaternary scheme corridor Edition)

Information Source Data gathered Application of information 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 proposed scheme corridor 1:50 000 Drift Edition – Underlying Geology - Drift deposits Sheets 11, 33, 34, 45, 46 along proposed scheme 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 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

Information Source Data gathered Application of information 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 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 3 is provided in Table 3-2.

Table 3-3-2 Utilities Authority Relevance to proposed scheme Northern Ireland Electricity Predominantly overhead lines, some underground cables

British Telecom Overhead and underground copper cables Underground fibre optic

Virgin Media Underground fibre optic Bytel Connections Underground fibre optic

Eircom UK Underground fibre optic NI Water Water service locations

3.2 Previous Ground Investigations

The records from a number of previous site investigations supplied by the Central Procurement Directorate and Geological Survey of Northern Ireland were obtained and included within the PSSR. Mouchel also hold records for a number of historical ground investigations. All historical ground investigation exploratory hole logs can be displayed on the GIS model. Drawing 796036- 0600-D-00062B shows the location of historical exploratory holes.

There is very limited historical GI information relating to the area in general, and only a few borehole records recording information which intersects the proposed scheme alignment directly. The information available relates to the peat bog immediately south of Seskinore Road and in the Ballygawley area associated with the A4 Annaghilla and A5 Corridor Improvement Proposed scheme.

The Preliminary Ground Investigation for the A5WTC was completed in March 2009 and is described in detail in the PSSR. The exploratory hole logs are hyperlinked within the GIS model.

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

3.3 Other Relevant Information

No other relevant geotechnical information pertinent to the proposed scheme has been obtained.

4 Field and Laboratory Studies

4.1 Walkover Survey

During preparation of the Preliminary Sources Study Report (PSSR) (796036/0600/R/007A, June 2009) a drive through survey was undertaken on 3rd 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 (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 Error! Reference source not found. .

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 proposed scheme. The locations of the preliminary ground investigation locations are shown on drawing 796036-0600-D-00062B. The main ground investigation was undertaken between September 2009 and April 2010 to investigate the proposed scheme. The locations of the main ground investigation locations are shown on drawing 796036-0600-D-00095A.

The individual earthwork splits are shown on drawing 796036-0600-D-00097A.

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 scheme alignment in order to obtain:

• a detailed knowledge of the stratigraphy along the proposed scheme;

• 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

• Reliable derivation of material parameters.

• 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), part of Environmental Services Group Limited (ESGL). This investigation comprised windowless sampling and dynamic probing and Cone Penetration Testing, investigation a number of route options.

The main ground investigation was designed, specified and monitored full time by Mouchel and undertaken between September 2009 to April 2010 by Soil Mechanics.

Due to access constraints and changes in route alignment during the main GI was undertaken in three phases:

Phase 1 – An initial first pass through the entire section to attain an overview of ground conditions. Phase 1 exploratory holes comprised cable percussive boreholes (CP) with rotary coring follow on in selected locations, trial pitting and Cone Penetration Testing (CPT). Groundwater monitoring equipment was installed in selected boreholes.

Phase 2 – A more detailed investigation of the entire section. The Phase 2 exploratory holes consisted of CP boreholes with selected rotary core follow on and trial pits. Groundwater monitoring equipment was installed in selected boreholes. 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. Phase 3 exploratory holes consisted of CP boreholes with selected rotary core follow on, trial pits, windowless sampling, dynamic and Mackintosh probing. Groundwater monitoring equipment was installed in selected boreholes. Televiewer surveys were undertaken in selected boreholes at the locations of proposed rock cuttings.

The total figures for the preliminary GI are reported in the PSS report 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 Phase 1 BH 22 and 4 re-drills Rotary Follow on 14 Trial Pit 84 Windowless sample with 9 Dynamic Probe Dynamic Probe 6 CPT 5 Phase 2 BH 96 and 47 re-drills Rotary Follow on 72 Trial Pit 62 Windowless sample with 0 Dynamic Probe Dynamic Probe 0 © Mouchel 2010 25 718736//R/0600/008 Vol 1 of 11 A5 Western Transport Corridor – Section 3 Ground Investigation Report – Volume 1 Introduction and Job_Name4 General Principles

Mackintosh Probe 0 Phase 3 BH 144 and 32 re-drills Rotary Follow on 82 Trial Pit 61 Windowless sample with 13 Dynamic Probe Dynamic Probe 12 Windowless sample 1 CPT 3 Mackintosh Probe 24

The locations of exploratory holes relating to the Historical, Preliminary and Main Ground Investigations are shown on Drawing No’s 796036-0600-D-00062. 796036-0600-D-00067B and 796036-0600-D-00095A.

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

Particular details of the investigation and groundwater regime carried out at each structure and earthwork location are recorded on the earthwork/structure summary sheets in Volumes 2 to 9. The earthwork and structure locations are identified on Drawing No’s 796036-0600-D-00097A and 796036-0600-D-98A.

An additional phase of GI is currently being carried out (Oct 2010) to infill areas not previously investigated due to road alignment changes, re-location of structures and to gain additional information at areas of soft compressible ground. The records and results from this additional phase of GI but will be incorporated in an updated version of this report.

4.3.2 Soil Sampling

Extraction of undisturbed 100mm diameter samples in boreholes was attempted at 1m intervals up to 10m depth and 1.5m intervals thereafter (alternate with SPT’s) in cohesive material. The U100 sampler was used to enable drivability through the clays due to the high granular content. The granular nature of the soils also resulted in a limited number of undisturbed samples recovered. Where sample recovery was poor Standard Penetration

Tests (SPT’s) were carried out directly after the undisturbed sample was attempted.

Representative bulk samples were taken from boreholes at 1m intervals, from trial pits at 1m 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 SPT’s.

Windowless samples were recovered in liners and later split for logging and sampling 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 and stored in wooden core boxes on recovery.

Environmental samples were taken from trial pits at specified locations on Greenfield land to prove that soil samples were chemically suitable and anywhere contamination was suspected. In addition, samples were also taken at intervals in areas of cut for waste acceptance criteria assessment. The environmental sampling comprised a 1kg tub sample and a 250g 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 12No exploratory holes, consisting of both window samples and boreholes to a maximum depth of 22m.

Groundwater monitoring instrumentation was installed in 72 boreholes, with 28 19 mm standpipe piezometers and 44 50mm standpipes. Groundwater monitoring instrumentation was installed at approximately 300m centres along the proposed scheme alignment, more frequently at proposed earthwork locations, proposed culverts and at locations of major structures.

The details and findings from the groundwater monitoring are summarised and discussed further in the relevant subsection 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. Y9044) 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’s) were carried out in boreholes in accordance with BS EN ISO 22476-3, in order to assess the relative density of the granular soils. SPT’s were also undertaken alternately with U100 samples in cohesive strata or where undisturbed samples could not be recovered. 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.

A limited number of hand shear vanes were undertaken in the trial pits in cohesive strata with results presented on the trial pit logs.

Dynamic Probing was undertaken in accordance with BS EN ISO 22476-2 at locations of suspected soft ground and adjacent to Windowless Sample holes. Handheld Mackintosh Probing was undertaken in areas inaccessible by conventional windowless sampling and dynamic probing.

Falling head permeability tests were undertaken in select boreholes in accordance with BS 5930:1999

The results of the in situ testing are presented in the Soil Mechanics Factual Report (Ref: Y9044) and are also hyperlinked to the exploratory locations in the GIS model. Interpretation of 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 proposed 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) Ref 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

Laboratory testing schedules were completed by Mouchel for determination of geotechnical parameters, assessment of environmental chemistry and determination of waste acceptability criteria. . A summary of all testing undertaken is given in Table 4-3 below.

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 and 4.5kg), moisture condition value (single point and 5 point moisture content relationship), 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 include; pH, water soluble sulphate and organic matter content.

The results of testing for contamination and waste acceptance criteria are discussed in Volume 10 of this report.

Where possible, unconsolidated undrained triaxial, shear box and oedometer testing was undertaken at proposed structure and embankment locations. However, the limited number of undisturbed samples recovered meant that the most suitable samples tested were not limited to the above sites.

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

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. samples scheduled

Classification/Compaction

Moisture Content BS1377: Part 2: 1990 1261

Liquid / plastic limits BS1377: Part 2: 1990 982 / 942

Bulk Density BS 1377: Part 2: 1990 601

Dry Density BS 1377: Part 2: 1990 241

Particle Density BS 1377: Part 2: 1990 98

Particle Size Distribution BS1377: Part 2: 1990 750 (wet sieving method)

Determination of dry BS1377: Part 4: 1990 31 density/moisture content relationship (2.5kg rammer)

Determination of dry BS1377: Part 4: 1990 32 density/moisture content relationship (4.5kg rammer)

Recompacted California BS1377: Part 4: 1990 98 Bearing Ratio (single point)

Recompacted California BS1377: Part 4: 1990 2 Bearing Ratio (5 point)

MCV (single point) BS1377: Part 4: 1990 349

MCV (multiple point) BS1377: Part 4: 1990 74

Los Angeles Abrasion BS EN 1097-2: 1998 24 Value

Strength / Consolidation

Unconsolidated BS1377: Part 7: 1990 105 Undrained Triaxial (total) strength

Consolidated Undrained BS 1377: Part 7: 1990 51 Triaxial (total) strength

Consolidated Drained BS 1377: Part 7: 1990 8 Triaxial (total) strength

Shear Box (effective BS1377: Part 7: 1990; Method 4 16 strength) (2.5kg rammer)

Shear Box (effective BS1377: Part 7: 1990; Method 4 4 strength) (4.5kg rammer)

1-D oedometer BS 1377: Part 5: 1990 35

Chemical (tests on soils and groundwater)

pH, water soluble BS1377:part 3:1990:clause 9 267 / 141 sulphate BS1377:part 3:1990:clause 5.5

Organic Matter Content BS 1377: Part 3: 1990 62

4.8.2 Copies of Test Results

Copies of all laboratory test results are included as part of the Soil Mechanics Factual Reports; (Main GI Report Ref: Y9044 and Preliminary GI Report Ref: Y9901).

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

5 Ground Summary

This chapter provides a general description of the ground summary. More detailed ground summaries are provided within volumes 2 to 9 of this report and for more information regarding the site refer to the PSSR (Ref: 796036/0600/R/007)

5.1 Geography

Section 3 is situated within County Tyrone, in the west of Northern Ireland extending from south west of Omagh in the north (CH 61480) to Moy Bridge where the existing A5 meets the N2 at the Irish border south of Aughnacloy (CH 93140). The proposed scheme was selected in July 2009 from four proposed alignments and is generally situated to the west of the existing A5. Drawing 79603-0600-D-00061B shows the proposed scheme as it passes south west of Omagh to south of Aughnacloy.

The proposed scheme bypasses a number of small towns and villages, the most notable of these are Ballygawley and Aughnacloy, which are the two main settlements along the proposed scheme located towards the southern end of the section. Minor settlements are evident at Newtownsaville and Eskragh to the west of the proposed scheme and at Seskinore situated along the B46, also to the west of the proposed scheme. Land use along the new alignment is predominantly farmland used for arable and grazing purposes.

Ballygawley is located in the south of the section between CH 82800 and CH 83400, and is the second largest town that the proposed scheme bypasses. The existing A5 bypasses the town to the west at Ballygawley roundabout, whilst the proposed scheme now bypasses the town to the west of the existing Ballygawley roundabout.

Aughnacloy is the largest town which the proposed scheme bypasses and is located in the southern end of the proposed scheme between CH 90500 to CH 92400. The existing A5 runs through the town, whilst the proposed scheme runs through agricultural land in a loop to the east of the town.

5.2 Topography

The topography along the proposed scheme is a function of the glacial environment in which the superficial strata were deposited. Other influences include hydrological and human factors. A relief map of the topography has

been provided in drawing 796036-0600-D-00068B with elevations indicated by 10m contours. Drawing 796036-0600-D-00069B provides an indication of slope steepness along the proposed scheme, with a colour coded system used for ranges of slope angle.

The northern extent of the proposed scheme, from south of Omagh to Gortaclare/Moylagh (CH61480 to CH68700) lies within the Omagh Farmlands Landscape Character Area (LCA) and is a lowland drumlin landscape. The poorly developed drumlins are typically between 5-10m high and 50-200m wide with side slopes generally between 1v:10h and 1v:5h Inter drumlin areas are low lying and less than 100m OD. The drumlin landscape gives way to high ground towards the east away from the proposed scheme. Drumlin topography also becomes less pronounced to the south and south east of the area as the ground rises towards the Slievemore Ridge.

The Gortaclare to Ballygawley region is dominated by the Slievemore Ridge with ground levels generally above 100m OD. The north facing slopes of this ridge fall at a shallow gradient towards Omagh and are cut by broad shallow valleys of the Eskragh Water and Garvaghy Water. Conversely, the south east facing slope, which is fault controlled, is typically of 1v:5h gradient, locally as steep as 1v:3h. The ridge is crossed by a number of valleys and natural passes, one of which has been adopted by the current A5 alignment north west of Ballygawley, and by other minor roads including the B83 and B186.

The Clogher Valley and Aughnacloy area comprises densely concentrated drumlins in the Clogher Valley. The drumlins here are well developed and exhibit greater height than around Omagh, with heights up to 20m and side slopes of 1v:8h to 1v:5h. Deep inter drumlin areas are often infilled with soft soils and in some locations are linked by small rivers and streams. The valley is crossed by the Ballygawley Water and Blackwater River, both of which have locally broad flat flood plains.

5.3 Historical Development

Historical mapping covering the proposed scheme and study area was obtained from the Ordnance Survey of Northern Ireland and Public Records Office for Northern Ireland. The mapping conveys the historical development of the study area since 1830 to present day and a summary is provided below. More details are contained in the PSSR.

During the 19 th Century, industry predominantly comprised corn and flax mills, located across the area. Numerous gravel pits are shown on the mapping of 1834 and later appear as scars in the landscape. By 1960 the milling industries

had diminished across the landscape, and many of the small gravel pits and quarries infilled.

The Clogher Valley Railway ran west to east from Clogher to Ballygawley and then south to Aughnacloy in the early 20 th Century, but is disused with many parts reclaimed and redeveloped by the 1960’s.

Some industrial development has occurred in close proximity to residential centres particularly around Aughnacloy with modern light engineering identified in current mapping.

A number of rivers have had their course altered and straightened for agricultural purposes, and where loughs have reduced in size bog land is now a feature.

5.4 Man-made Features – Mining and Quarrying

A limited number of small backfilled quarries and gravel pits are located under the proposed scheme footprint. The main locations are at Moylagh Junction (CH 68660), west of Old Chapel Road (CH 87750) and east of Old Chapel Road (CH 88030). The landfill at Tullyvar is adjacent to but not affected by the proposed scheme. There is a second recorded landfill SE of Aughnacloy, that is adjacent to, but not affected by the scheme.

5.5 Hydrology

The proposed scheme crosses a number of designated watercourses including Ranelly Drain, Letfern, Routing Burn, Roughan, Ballygawley Water, Tullyvar and Lisadavil burns. There are also numerous minor, mainly undesignated watercourses that are crossed by the proposed scheme. For more information on these watercourses refer to the Section 3 PSSR (Ref: 796036/0600/R/007).

5.6 Geology

This section presents the general geology and hydrogeology across the whole proposed scheme. A detailed description is presented in volumes 2 to 9 of this report.

5.6.1 Superficial Geology

Superficial geology along the proposed scheme is dominated by glacial deposits comprising glacial till and glacio-fluvial sand and gravel, laid down during the last glaciation of Ireland, between 10,000 and 70,000 years ago. More recent alluvial and organic deposits occur in isolated pockets throughout the proposed scheme overlying the glacial deposits. These include peat, alluvium and lacustrine deposits. A map of the superficial geology for Section 3 is provided in drawing 796036-0600-D-00078B.

Topsoil is generally around 0.3m thick with localised areas up to 1m deep. There is very little presence of Made Ground, but, where it was encountered thicknesses varied between 0.4m and 2.8m. Made Ground is encountered in isolated small areas, possibly as a result of unofficial landfilling. Further information on Topsoil and Made Ground is provided in the Section 3 PSSR (Ref: 796036/0600/R/007) and in Volumes 2 to 9 of this report.

Peat

Peat was encountered at discrete locations along the proposed scheme ranging in thickness from 0.2m to 7.0m as both raised peat deposits and fen deposits. These deposits are identified in the published geology around Seskinore Road, Doogary and Newtownsaville. Raised peat forms the majority of the peat deposits encountered during the main ground investigation, are generally found in greater thickness than fen peat. Raised peat deposits are generally associated with glacio-lacustrine environments and are therefore found overlying lacustrine deposits, described later in this chapter.

The specific areas of peat deposits are discussed within volumes 2 to 9 of this report.

Alluvium

According to published geology alluvium occurs in areas associated with existing designated watercourses or historic watercourses, predominantly in the area of Rannelly Drain, Letfern, Routing Burn, Roughan, Ballygawley Water, Tullyvar and Lisadavil.

Alluvium was encountered during the main ground investigation within the areas indicated by the published geology and ranged in thickness from less than a metre up to 16.75mbgl at Ballygawley Water. Any deep pockets of

alluvium are localised mainly associated with floodplains or drumlins. Further detail on specific areas of alluvium can be found in volumes 2 to 9 of this report.

Lacustrine Deposits

Published geology indicates lacustrine deposits (also known as lake alluvium), along the proposed scheme at Tullyrush Road. Lacustrine deposits are considered to have been formed in post-glacial lake environments.

The main ground investigation identified several pockets of lacustrine deposits, predominantly south of Slievemore Ridge, that were not indicated on published geology. The thickness of these Lacustrine Deposits ranged between less than a metre to 7.6m. Further discussion on the Lacustrine Deposits can be found in volumes 2 to 9 of this report.

Glacial Till

Glacial till deposits along the proposed scheme are the most abundant of all the superficial deposits. They are described in the published geology and from historical borehole records as soft to firm sandy gravelly clay and silt with cobbles and boulders, with bands of medium dense to dense clayey silty sand and gravel. The thickness of deposits range from 1m to more than 35m deep with average thicknesses encountered around 2.5mbgl. The greatest thicknesses are mainly localised and associated with drumlins.

Information obtained from the ground investigation confirms what was anticipated from the published geology and the historical borehole records. Further description and interpretation of glacial till deposits can be found in volume 2 to 9 of this report.

Glacio-fluvial Sand and Gravel

Published geology indicates glacio-fluvial sand and gravel to be present along the proposed scheme in small pockets at a few locations; Drumconnelly Road, north west of Newtownsaville, Rarogan Road, south west of Ballygawley, and east of Aughnacloy. These deposits are located in the vicinity of current and historic watercourses, although deposition is associated with glacial water courses. The thickness of the deposit, as observed by the main ground investigation, ranges from 1.8m to 3.8m.

The main ground investigation confirmed that glacio-fluvial sand and gravel deposits corresponded with that anticipated from published geology.. More detail on these deposits can be found in volumes 2 to 9 of this report.

5.6.2 Solid Geology

Solid geology varies significantly along the proposed scheme and has varied characteristics. The underlying geology is structurally complex and controlled by three major faults:-

• The Tempo-Sixmilecross Fault and Killadeas –Seskinore Fault in the north (both of these join around Moylagh) and

• The Clogher Valley Fault ( a complex of several minor faults) in the south

These break the strata up into 3 principal provinces:

• Devonian age formations in the north (Shanmullagh Fm)

• Carboniferous age formations in the centre (Gortinfinbar Formation) forming the high ground around Tycanny.

• Further Carboniferous age formations in the south (a complex of small outcrop patterns in the Clogher Valley).

Because of faulting, the age relationships of the various strata is not clearly defined, but the following descriptions are in approximate age of oldest first. A map of the solid geology for Section 3 is provided in drawing 796036-0600-D- 00077B.

Shanmullagh Formation (CH 61480 to CH 68290)

The Shanmullagh Formation is described in the published geology as red interbedded sandstones, siltstones and mudstones of Devonian age, and is indicated to be present to the south of Omagh. The formation is separated from the Omagh Sandstone Group by the Omagh Thrust Fault which lies on a north east – south west orientation through the centre of Omagh.

The formation was encountered beneath superficial deposits at depths between 4m bgl and 13.2m bgl. The maximum proved thickness of this formation was 5.35m. Refer to volumes 2 to 9 for further details of this formation.

Ballinamallard Mudstone Formation (CH 68290 to CH 68620)

The Ballinamallard Mudstone Formation is described in the published geology as a grey red mudstone and siltstone, and is evident as a small wedge to the east of Seskinore. This was confirmed during the main ground investigation.

The formation was encountered beneath superficial deposits at depths between 3.67m bgl and 6m bgl. and was proven to a depth of 11m bgl. Refer to volumes 2 to 9 for further details of this Formation.

Raveagh Formation (CH 68620 to CH 69600)

The Raveagh Formation is described in the published geology as red brown fine conglomerate and sandstone of Devonian age, and is indicated to be located to the south east of Seskinore as a thin wedge. This was confirmed during the main ground investigation.

The formation was encountered beneath superficial deposits at depths between 2.8m bgl and 17.7m bgl. and was proven to a depth of 24.4m bgl. Refer to volumes 2 to 9 for further details of this Formation.

Gortfinbar Conglomerate Formation (CH 69600 to CH 78890)

The Gortfinbar Conglomerate Formation is described in the published geology as purple brown conglomerate, containing mainly volcanic cobbles, with some quartzite and sandstone, and is indicated to the south of the Shanmullagh Formation, with the boundary along the Killadeas – Seskinore Fault. This was confirmed during the main ground investigation.

The formation was encountered beneath superficial deposits at depths between 0.7m bgl and 19m bgl, and was proven to a depth of 30m. Refer to volumes 2 to 9 for further details of this formation.

Ballyness Formation (CH 78890 to CH 80300 & CH 83960 to CH 85130)

The Ballyness Formation is described in the published geology as red and purple red sandstone and conglomerate and is visible to the north of Ballygawley as many wedges between two fault lines. This was confirmed during the main ground investigation.

The formation was encountered beneath superficial deposits at depths between 0.1m bgl and 16m, and was proven to 21m bgl. Refer to volumes 2 to 9 for further details of this Formation.

Clogher Valley Formation (CH 80300 to CH 81035 & CH 83050 to CH 83960)

The Clogher Valley Formation is described in the published geology as fossiliferous mudstone, siltstone, sandstone and crinoidal limestone. It is recorded to the north of Ballygawley as many wedges between two fault lines. This was confirmed during the main ground investigation.

The formation was encountered beneath superficial deposits at depths between 1.9m bgl and 17m bgl, and was proven to 21m bgl. Refer to volumes 2 to 9 for further details of this Formation.

Maydown Limestone Formation (CH 81035 to CH 83050, CH 85130 to CH 90270 & CH 92000 to CH 93140)

The Maydown Limestone Formation is described in the published geology as a limestone formation with abundant corals and brachiopods, and is indicated to occur in small outcrops to the north west and south of Ballygawley down to Aughnacloy.

The formation was encountered beneath superficial deposits at depths between 0.25m bgl and 11.7m bgl and was proven to a depth of 24.2m bgl. Refer to volumes 2 to 9 for further details of this Formation.

Carrickaness Sandstone Formation (CH 90270 to CH 91285)

The Carrickaness Sandstone Formation is described in the published geology as coarse grained, pebbly lithic sandstone, and is encountered as a wedge to the east of Aughnacloy, spreading west towards the town.

The formation was encountered beneath superficial deposits at depths between 3.5m bgl and 8.5m bgl, and was proven to a depth of 12.5m bgl. Refer to volumes 2 to 9 for further details of this Formation.

Bundoran Shale Formation (CH 91285 to CH 92000)

The Bundoran Shale Formation is described in the published geology as a dark grey mudstone, with siltstone and calcareous fossiliferous limestone, and is recorded as a wedge to the south east of Aughnacloy.

The formation was encountered beneath superficial deposits at a depth 5m bgl, and was proven to a depth of 7m. Refer to volumes 2 to 9 for further details of this formation.

As each of the formations are of substantial thickness there were no instances recorded where drilling had progressed through one bedrock stratum to encounter another.

5.7 Hydrogeology

The hydrogeology baseline study was based on the following information:

• Results of the ground investigation undertaken by Mouchel between September 2009 and spring 2010;

• 1:250 000 Geological Map of Northern Ireland (Solid and Drift Editions);

• Water Framework Directive (2000/60/EC) Aquifer Classification Scheme for Northern Ireland – Geological Survey of Northern Ireland (2005);

• Groundwater Vulnerability Map;

• A groundwater vulnerability screening methodology for Northern Ireland. Groundwater Management Programme, Commissioned Report CR/05/103N, 2005.

The aquifer classification comprises eight classes of aquifer based on geological strata type (bedrock/superficial), relative resource productivity (high/moderate/limited/poor) and flow type (fracture/intergranular).

The groundwater vulnerability classification comprises classes 1 to 5, with 1 being the least vulnerable and 5 the most vulnerable, and 5 sub-classifications (4a to 4e) to take account of differing superficial deposits. The vulnerability ratings are determined by:

• The depth to the water table in highly permeable superficial aquifers;

• The depth to the water table in intergranular and dominantly intergranular- flow bedrock aquifers;

• Soil permeability;

• Superficial deposits permeability;

• Superficial deposits thickness.

In addition:

• All areas within 30 m of a mapped point recharge feature such as karst will have a vulnerability rating of 5;

• Where drift is mapped as <1m thick the vulnerability class is always either 4 or 5;

• Where drift is mapped as <3m thick the vulnerability class is always 3, 4 or 5;

• No areas where drift is mapped as >1 m thick will have a vulnerability of 5, unless they are close to a mapped point recharge feature.

5.7.1 South of Omagh to Gortaclare

There is glacial till present across this section forming drumlins, although cover is patchy with bedrock exposed in places. Raised peat bogs are also present, particularly in the north. Alluvium and glaciofluvial deposits associated with the larger watercourses are considered to act as minor aquifers.

In the northern part of this section, the solid geology generally comprises Devonian sandstones and mudstones. The sandstones and mudstones present in this section are assigned an aquifer classification of ‘fracture flow, of moderate productivity, Bm(f)’.

The majority of this section is dominated by groundwater vulnerability Class 2 largely as a result of the extensive low permeability superficial deposits, mostly glacial tills, or peat. Areas with high permeability superficial deposits have been assigned Class 4, these are mainly in areas where deposits consist largely of River Alluvium and glacio-fluvial sands and gravels.

5.7.2 Gortaclare to Ballygawley

Alluvial deposits are present associated with the rivers and glaciofluvial deposits in the vicinity of Newtownsville, Roscavey and Garvaghy. Elsewhere the covering of glacial till is thin or non-existent.

The Carboniferous and Devonian sandstones and mudstones present in this section are again classified as Bm(f), ‘fracture flow, of moderate productivity’.

The proposed scheme crosses a region of moderate permeability deposits, mainly glacial till material, giving a vulnerability Class of 3. This is dissected by areas of high permeability deposits and exposed bedrock, leading to increased vulnerability classifications of 4 or 5 at these sections.

5.7.3 Ballygawley to Aughnacloy

Alluvial and glaciofluvial sands and gravels are mainly associated with the water courses in this section with cohesive or granular glacial till present elsewhere. The geological map indicates there to be areas of exposed bedrock along much of this section, although superficial deposits were encountered in all exploratory holes drilled in this area.

Significant groundwater flows occurs in the glacial sands / gravel deposits and in coarse grained alluvial strata. The sandstones and limestones which underlie this section are also classified as being of moderate productivity (Bm(f)) with fracture flow being predominant and yields being dependent on the presence of fractures.

The vulnerability of the superficial deposits in this section is predominantly dominated by vulnerability Class 2 largely as a result of the extensive low permeability superficial deposits, comprising mostly glacial tills. Areas with high permeability superficial deposits have been assigned Class 4 as these are mainly in areas where deposits consist largely of River Alluvium and glacio- fluvial sands and gravels.

Further discussion on the hydrogeology of the superficial deposits can be found in the Section 3 PSSR (Ref: 796036/0600/R/007) and in Volumes 2 to 9 of this report.

6 Ground Conditions and Material Properties

6.1 Introduction

The proposed scheme 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 9.

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 9, 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: c h values derived from t 50 values (after Robertson et al 1992)

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):

2 E=17.6(CBR) 0.64 MN/m Equation 6-4

Where CBR= Californian Bearing Ratio and is given as a %.

E will be E’ or Eu 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 c u 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:

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

φ' 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: φ' 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:

φ' =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 this equation 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.

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 6-15 (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.

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 N value 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 6-16 Using the Stroud correlation this can therefore be related to N value using the following equation.

2 E’= f 2N (MN/m ) Equation 6-17

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- e1)/log( σ’1/ σ’0) Equation 6-18

Skempton, 1944, proposed the following relationship for C c and Liquid Limit for normally consolidated clays.

Cc=0.007(LL-10) Equation 6-19 Terzaghi and Peck developed a similar correlation for low and medium plasticity clays which is valid for a sensitivity of up to 4 and a maximum liquid limit of 100.

Cc=0.009(LL-10) Equation 6-20 Sensitivity is the relationship between natural shear strength to remoulded shear strength and can be determined from liquidity index using the chart in Figure 6-9.

Figure 6-9: Correlation between sensitivity and liquidity index (after Cater and Bentley, 1991)

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 Ip = plasticity index and G s= specific gravity.

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 peats are upland deposits laid down in areas where precipitation exceeds evaporation (ie blanket bog) whereas fen peats tend to be low lying peats formed in areas of poor drainage. It is considered that the peats 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 recompression of over consolidated materials at stresses less than the pre consolidation pressure. Carter and Bentley, 1991 state that it is often assumed to be:

Cr= 5-10% C c 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 cu 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.

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

Table 6-7: Equilibrium Subgrade CBR Estimation 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 6-10.

Figure 6-10: 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( + ) 1+ e (( 60 +15 D−GSI 11/) )

Equation 6-34

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 proposed scheme, 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

Geotechnical Risk Register is included in Volume 11 of this report.

8 Basic Design Philosophy and Methodology

8.1 Introduction

In order to progress the proposed scheme to specimen design and develop alignments, structures, vesting / direction orders and a cost estimate, some outline geotechnical design work has been required. Although geotechnical design of the proposed scheme is subject of the Geotechnical Design report (GDR), the purpose of that report is to record the detailed design of the proposed scheme. Therefore 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 proposed scheme in order to provide best value. 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.

The designs have been refined as necessary to suit site specific conditions and are modified, as 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 proposed scheme:

Cuttings - 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 - both sides of the earthwork are in fill. They may be asymmetric as above.

Side long ground where 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 have stability issues, often requiring a shallower slope.

Earthworks less than 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 of the earthwork becomes part of a cutting or embankment.

8.1.2 Groundwater

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 20kN/m 2 has modelled throughout on the footprint of the road with a surcharge of 10kN/m 2 on verges and above the slopes to model agricultural traffic and other activities at the top of slopes.

Unless otherwise stated a c’ of 1kN/m 2 has been used in all base line slope analyses in over consolidated 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.

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

Slopes greater than 10m high will require a berm at least 2m wide at mid height to maintain stability. The berm should slope outwards at minimum cross-fall 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 1930’s and the 1970’s 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 it is recommended that this is 1m wide for every 1m height of slope, up to a maximum width of 4m. More detailed design of the rock catch ditches can be carried out using methods such as that given on Figure 8-2

• At 10m intervals a 4m 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 superficial deposits a 4m wide berm is recommended at the interface with a drainage ditch to intercept any surface run off and ground water in the drift deposits. The berm can be reduced in width to 2m for rock slopes less than 4m high. The safe slope angle for the superficial 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 4m to construct the slope at an angle of 1v:2.5h without a boulder trench rather than construct it at 1v:1h with a boulder trench, which will be up to 4m wide. Above 4m 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 impact of high water table 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 50kPa, which is considered to be a lower bound practical figure for constructing earthworks using remoulded cohesive glacial tills.

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

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

An HB loading of 20 kN/m 2 has been modelled on the carriageway 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, increasing stability and accelerating consolidation. The starter layers would typically be 0.6m 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 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 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 material. 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 infilling inter drumlin areas and also larger raised peat bogs.

If peat deposits are less than 4m deep, and in short lengths up to 5m 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 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 (Au gust, 2010) has indicated that in many cases, deep inter-drumlin fen deposits consist of less than 3m peat, underlain by normally consolidated clays, silts and sands. 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. Where piled embankments are used, then measures must be put in place to protect the piles from future surcharge and/or lateral loading which could result in their 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 2-3m 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 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 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, although this may prove uneconomic. Within Ireland it is understood that that AES Kilroot Power Station, County Antrim and Moneypoint

Power station, County Clare 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, including Maxit, polystyrene and 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 structures sensitive to settlement with more economic conventional fill materials 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 across 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 0.5m above maximum predicted flood levels.

8.2.3 Re-use of Materials

Reusability 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 Specification for Highway Works.

For cohesive material 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 30-50kN/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 - 200kN/m 2. However, class 2C stony cohesive material 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.

Re-use potential has been analysed by review of natural moisture content (NMC), optimum moisture content (OMC) from compaction tests, undrained shear strength, moisture condition values (MCV’s) and Californian Bearing Ratio (CBR) tests.

These results have been reviewed as relationship packages to determine an overall percentage re-use for each section. Although individual analyses varied from section to section a typical analysis package included NMC and

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 2 correlated with a c u of 50 - 150kN/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 minimum and maximum moisture contents obtained could then be plotted onto a NMC vs MCV graph to determine an acceptable range of MCV’s. 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 MCV’s were checked to ensure that there were no data errors.

The recorded NMC and MCV values were then plotted as frequency curves and the percentage 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 less than 2%, a c u of less 50 kN/m 2, a NMC greater than optimum moisture content plus 2%, or a soil with a MCV less than 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 may be carried out 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 locations:

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

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

• Ditches at the toe of embankments to control run off and maintain stability of the embankment. The ditches should be placed at least 2m 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 glacial till materials during adverse weather conditions.

Glacial tills frequently contain discontinuous water bearing 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 out cause lack of support for overlying materials. Allowance should therefore be made for the installation of herringbone, counterfort 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 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 Error! Reference source not found. ) 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 groundwater at 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 achieved. It is recommended that 210mm of capping is used to improve the CBR value to 15%.

Where embankments are constructed from 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

Discussion of any contaminated land is contained within Volume 10 of this report.

8.8 Ground Treatment Including Treatment of any Underground Voids etc.

8.8.1 Soft Spots

At grade sections where soft spots are encountered (CBR<2.5% or c u <50 kPa) should be excavated out and replaced with Class 1, 2 or Class 6 material. If 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

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

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

6.17. 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.

6.18. 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

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

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

6.21. 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

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

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

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

6.25. 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

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

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

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

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

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

8.3.

Appendix A Geotechnical Certificate

Geotechnical Certificate

Scheme Title – A5 Western Transport Corridor Certification Ref GW163

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

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 cer tificate 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//R/0600/008 Vol 1 of 11 Ground Investigation Report

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: 30 th October 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 Guide to Navigating the GIS Model

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 Locations exploratory hole locations are hyperlinked within this drawing. 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 Notes & Photographs and 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 Photographs Reports 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 terrain 100m 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. 796036-0600-D-00080B Groundwater The groundwater vulnerability map indicates the significance of pollution incidents occurring to the underlying aquifers. Vulnerability Map

Drawing Number Drawing Title Description of Drawing

796036-0600-D-00095A 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-00096A Extent of each GIR Geographical extent covered by each of the GIR volumes volume 796036-0600-D-00097A Earthwork split Drawing provided to display the labelling and details of the earthworks along the route alignment. 796036-0600-D-00098A Structures locations and This drawing is provided to display the locations of all structures along the alignment and hyperlinks to display detailed datasheet hyperlinks summaries of each. (incl culverts, retaining structures and attenuation ponds) 796036-0600-D-00099A 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 Western Transport Corridor – Section 3 Ground Investigation Report – Volume 1 Introduction and Job_Name4 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 Western Transport Corridor – Section 3 Ground Investigation Report – Volume 1 Introduction and Job_Name4 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