Section 1, New Buildings to South of Strabane

Ground Investigation Report – Volume 1 Introduction and General Principles

September 2010

Document Ref No 718736-0600-R006 Volume 1 of 13

For Department for Regional Development

Road Service Ref GW163

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

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

Document Control Sheet

Project Title A5 Western Transport Corridor

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

Report Reference 718736-0600-R-006 Volume 1 of 13

Version A

Issue Date September 2010

Record of Issue

Version Status Author & Date Checked & Date Authorised & Date

A For J Vickers - 24/09/10 K Innes - 24/09/10 D Towell - Comment 24/09/10

A Wheeler -

24/09/10 M Howard - 24/09/10

A Tucker - 24/09/10

Distribution

Organisation Contact Format Copies

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

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

Jacobs L Davison pdf 1

(On behalf of RS HQ)

Mouchel P Carey - Section 1 Project pdf 1 Manager

Mouchel D Parody - Project pdf 1 Manager

Bbm W Diver pdf 1

Table 1-1 Geotechnical Reports – List of Volumes GIR Report Number Title Start End Volume CH CH 1 718736-0600-R-006 Introduction and General 0 22800 Volume 1 of 13 Principles

2 718736-0600-R-006 Findings of the 0 6560 Volume 2 of 13 Investigation, Section 1A

3 718736-0600-R-006 Findings of the 6560 7260 Volume 3 of 13 Investigation, Section 1B

4 718736-0600-R-006 Findings of the 7260 9870 Volume 4 of 13 Investigation, Section 1C

5 718736-0600-R-006 Findings of the 9870 12340 Volume 5 of 13 Investigation, Section 1D

6 718736-0600-R-006 Findings of the 12340 17040 Volume 6 of 13 Investigation, Section 1E

7 718736-0600-R-006 Findings of the 17040 18680 Volume 7 of 13 Investigation, Section 1F

8 718736-0600-R-006 Findings of the 18680 19550 Volume 8 of 13 Investigation, Section 1G

9 718736-0600-R-006 Findings of the 19550 20880 Volume 9 of 13 Investigation, Section 1H

10 718736-0600-R-006 Findings of the 20880 21300 Vol 10 of 13 Investigation, Section 1I

11 718736-0600-R-006 Findings of the 21300 22800 Volume 11 of 13 Investigation, Section 1J

12 718736-0600-R-006 Environmental Testing 0 22800 Volume 12 of 13 Analysis

13 718736-0600-R-006 Risk Register 0 22800 Volume 13 of 13

This volume is the volume highlighted in bold

LIMITATIONS

This report is presented to the Roads Service in respect of the A5 Western Transport Corridor (WTC) – Section 1 and may not be used or relied on by any other person or by the client in relation to any other matters not covered specifically by the scope of this Report.

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

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

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

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

Contents

1 Executive Summary...... 10 2 Introduction...... 12 2.1 Description of the Project...... 12 2.2 Scope and Objective of the Report ...... 18 2.3 Geotechnical Category of Project ...... 21 2.4 Other Relevant Information...... 22 3 Existing Information ...... 23 3.1 Sources of Information...... 23 3.2 Previous Ground Investigations...... 26 4 Field and Laboratory Studies...... 28 4.1 Walkover Surveys...... 28 4.2 Geomorphological/Geological Mapping ...... 29 4.3 Ground Investigation...... 29 4.4 Drainage Studies...... 37 4.5 Geophysical Survey...... 37 4.6 Pile Tests...... 37 4.7 Other Field Work ...... 37 4.8 Laboratory Investigation ...... 38 5 Ground Summary ...... 41 5.1 Geography...... 41 5.2 Topography ...... 42 5.3 Historical Development...... 43 5.4 Mining and Quarrying ...... 44 5.5 Hydrology ...... 45 5.6 Geology...... 45 5.7 Hydrogeology ...... 48 5.8 Geomorphology...... 50 6 Ground Conditions and Material Properties ...... 51 6.1 Introduction...... 51 7 Geotechnical Risk...... 74 8 Basic Design Philosophy and Methodology...... 75 8.1 Introduction...... 75 8.2 Earthworks ...... 76 8.3 Highway Structures...... 92 8.4 Strengthened Earthworks ...... 93 8.5 Drainage...... 93 8.6 Pavement Design, Subgrade and Capping...... 94 8.7 Contaminated Land ...... 96 8.8 Ground Treatment Including Treatment of any Underground Voids etc..... 96 8.9 Specification Appendices...... 96 8.10 Instrumentation and Monitoring ...... 96 Principal Symbols ...... 97 References...... 100

Tables

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

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

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

Table 2-3: Report Volumes ...... 19

Table 3-1: Sources of Information...... 23

Table 3-2: Statutory Undertakers (Utilities) ...... 26

Table 3-3: Previous Geotechnical Studies ...... 27

Table 4-1: Drawings showing locations of field survey data ...... 29

Table 4-2: Summary of Exploratory Hole Types ...... 31

Table 4-3: Summary of Exploratory Hole Types ...... 32

Table 4-4: Summary of Geotechnical Laboratory Testing...... 38

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

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

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

Table 6-4: Relationship between Cone Resistance, Phi and Young’s Modulus (Ref. Eurocode 7) ...... 57

Table 6-5: Critical Angle of Internal Friction from Plasticity Index (BS 8002)...61

Table 6-6: Overconsolidation Ratios (After Barnes, 2000) ...... 67

Table 6-7: Equilibrium Subgrade CBR Estimation...... 68

Table 6-8: Basic friction Angle on Discontinuities (after Barton and Choubey, 1977)...... 70

Table 6-9: Modular Ratios (After Hobb’s 1974) ...... 73

Table 6-10: Rock Mass Factors (After Hobbs, 1974)...... 73

Table 8-1: Geomechanics Classification of Jointed Rock Mass (after Bieniawski, 1976) ...... 79

Table 8-2: Typical µg Values (After Tomlinson, 2001)...... 84

Table 8-3: Diggability Index rating (after Trenter, 2001) ...... 92

Table 8-4: Excavation Diggability Classification (after Trenter, 2001)...... 92

Table 8-5: Principal Symbols...... 97

Figures

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

Figure 6-1: ch values derived from t50 values (after Robertson et al 1992)...... 52

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

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

Figure 6-4: CPT N Value Correlation...... 58

Figure 6-5: Terzaghi and Peck method for Calculating Allowable Bearing Pressure ...... 59

Figure 6-6: Angle of Internal Friction Determined from Plasticity Index ...... 60

Figure 6-7: Variation of f1 with Plasticity Index (after Tomlinson, 2001)...... 61

Figure 6-8: Variation of f2 with Plasticity Index (after Tomlinson, 2001)...... 63

Figure 6-9: Joint Roughness Co-efficient (After Barton & Choubey, 1977) ...... 71

Figure 8-1: Guidelines for the Design of Rock Traps (After Whiteside, 1986) ..80

Figure 8-2: Rock Slope Land Requirements ...... 81

Figure 8-3: Typical Section for Dig Out and Replace Sites ...... 86

Figure 8-4: Excavability of Rock (after Petitifer and Fookes, 1994 and Harber et al, 2000)...... 90

Figure 8-5: Diggability Chart (after Trenter, 2001) ...... 91

Appendices

Appendix A GIS Navigation Guide

1 Executive Summary

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

For logistical reasons the 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 Ground Investigation Report covers Section 1 only. Sections 2 and 3 are reported separately.

Section 1 of the A5 WTC is approximately 23 km long. From the village of New Buildings the route of the Proposed Scheme trends to the southwest near the River Foyle. It passes in cutting through Bready Hill and then continues south/southwest across the Foyle floodplain. The route then goes around the western side of the town of Strabane, one the banks of the River Finn, before continuing approximately due south across higher ground towards the Section 2 boundary at Sion Mills.

In Section 1 the central part of the Proposed Scheme is dominated by superficial deposits comprising alluvium. These generally consisted of soft organic clays and silts underlain in places with silty sands. The northern and southern parts are underlain by glacial till, moraine and glaciofluvial deposits comprising interbedded cohesive and granular deposits. The solid geology underlying the superficial deposits comprises the Ballykelly and Claudy Formations which comprise metamorphosed sandstone and mudstone.

There are a number of significant geotechnical risks and design issues associated with the Proposed Scheme’s topography and ground conditions. A significant rock cutting is proposed at Bready and there is an approximately 1.2km long cutting in rock to the south of Strabane. A significant bridge with large spans and approach embankments are proposed for the River Mourne crossing. Design will need to address issues where the route crosses floodplain areas with significant depths of soft and very soft alluvium. These will comprise total and differential settlement, earthworks slope instability, lateral movement and lateral loading of structure foundations. There are a number of localised sites where there have been potentially contaminative former land uses. These are generally associated with the former Great Northern Railway Line, the Strabane Canal and associated features, two disused landfill sites, old industrial sites around Strabane and sites with fly-tipping. The majority of the Proposed Scheme is however on Greenfield land.

The main ground investigation for the scheme was carried out on site from September 2009 to March 2010 and comprised 187 No. cable percussion boreholes, 45 No. with rotary follow on, 16 No. rotary holes, 178 No. trial pits, 17 No. window sample holes, 13 dynamic probe holes and 67 cone penetration tests.

Due to the size of Section 1 this Ground Investigation Report (GIR) has been split into 13 volumes. This Volume 1 covers the introduction and general principles. For Volumes 2 to 11, Section 1 has been split into 10 geographical area sub-sections with similar geology, topography and geotechnical issues. This allows the ground conditions, material properties and geotechnical recommendations to be reported in manageable volumes. There is then a volume for contamination and analyses of environmental testing results and a volume for 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.

Figure 2-1: Regional Context Plan

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

2.1.2 Scheme Objectives

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

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

2.1.3 Geotechnical Objectives

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

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

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

• The nature, distribution and thickness of rock strata

• Hydrogeological conditions

• Topography and geomorphology

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

• Watercourse crossings

2.1.4 Scheme Section

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

Table 2-1: Section Limits Section Section Limits

1 New Buildings to South of Strabane

2 South of Strabane to South of Omagh

3 South of Omagh to Aughnacloy

Each section has been designed and reported on separately. This report relates only to Section 1.

2.1.5 Development of the Scheme

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

The scheme evolved in three stages as follows:-

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

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

Stage 3 – development of a specimen design for the Proposed Scheme. 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 1 of the scheme.

2.1.6 Description of the route of the Proposed Scheme

The route of the Proposed Scheme is described below from north to south extending from the northern end of the village of New Buildings to approximately 200m north of Primrose Park Road on the north west of Sion Mills (CH 22800), south of Strabane.

In general the route is located to the west of the existing A5 throughout Section 1, with the exception of a short section near the village of Bready.

• The route starts at CH 0 along the existing A5, which runs between the village of New Buildings and the River Foyle.

• At approximately CH 350, and opposite the petrol filling station in the centre of New Buildings, the route leaves the existing A5 towards the south west, with a roundabout connection to the existing network.

• To approximately CH 3500 the route runs between the existing A5 and the River Foyle, being generally less than 250m from the river. The topography is gently undulating with sections of embankment and cutting. The route crosses a number of minor watercourses. At approximately CH 3200 the route passes between a sewage treatment works and the village of Magheramason.

• The route continues to the south west and passes under Dunnalong Overbridge at CH 3912.

• To CH 5800 the route crosses low lying ground. Along this section the route runs along the base of Gortmonly Hill, a foothill of the Sperrins.

• At approximately CH 5700 the route moves onto embankment as the road level rises and passes over the existing A5 at CH 6416. The route then runs to the east of the existing A5 for 2700m.

• The route enters a significant cutting from CH 6600 to CH 7250. This cutting is located at the far western edge of Gortmonly Hill to the east of the village of Bready.

• The route then runs due south on embankment across a low valley to CH 8250. The route passes under Donagheady Road Overbridge at CH 7752.

• The route continues along gently undulating ground to CH 9111 where it crosses back the east side of the existing A5.

• The route continues on embankment as ground level falls away. An underbridge is located at CH 10021 for Drummeny Road. The route is then carried on embankment across the Burn Dennet flood plain and the associated river bridge is located at CH 10506.

• After the river crossing, the existing A5 trends back towards the east to pass around McKeans Moss on a terrace of higher ground. The route is in cutting from approximately CH 11320 to CH 12340. It goes close to the village of Cloghcor and the existing A5. A bridge is proposed for Moss Road and Ballydonaghy Road at CH 11278.

• From CH 12340, at Leckpatrick, the route returns to embankment as it comes onto the main Foyle floodplain. The route crosses the Glenmornan River at CH 12720. It continues across the Foyle floodplain with varying embankment heights as the ground profile varies between the flat floodplain areas and slightly higher relief areas on the floodplain.

• The route continues to the west of Ballymagorry. A bridge is present at CH 13501 for Park Road. Ballymagorry junction and overbridge is proposed at CH 14721. A flood relief structure is proposed in the vicinity of Spruce Road between CH 14800 and 14900.

• The route then approaches the northern end of Strabane and runs between the existing A5 and the disused Strabane Canal. The route comes close to the northern end of Strabane Glen in the vicinity of Roundhill.

• The route crosses the disused Strabane Canal at CH 16750.

• Around Strabane the route is close to the existing A5 skirting the low lying western edge of the urban area. A viaduct is proposed across the River Mourne and approaches. This crossing is centred at approximately CH 17920. Junctions are proposed to the north and south of the river. To the north is a junction with Lifford Road (A38), the existing A5 and Railway Street (B73). To the south is a junction again with the existing A5 and with Bradley Way.

• The route continues due south west along the bank of the River Finn. To the south of CH 18750, it is typically 100m from the river. The route follows the former County Donegal Railway corridor. A junction is proposed at CH 19480 which is a proposed tie in with the link to the N15/N14 “Lifford Link” across the River Finn.

• At CH 19480 the route then turns sharply to the south by way of a roundabout junction and enters a significant cutting as ground level rises at Carricklee Hill. The route passes over Urney Road at CH 19510. This cutting continues to CH 20900 beyond the west and south west extent of the Strabane urban area. Strahans Road Overbridge is located at CH 20371 and the route continues in cutting adjacent to the flooded Strahans Road Quarry from CH 20440 to CH 20630.

• The route continues on a low embankment or at grade from CH 20900 to CH 21300. The route again enters a significant cutting for approximately 630m to CH 21930. Orchard Road Overbridge is present at CH 21413.

• The route is on low embankment from CH 21930 to CH 22250 with Peacock Road Junction Overbridge at CH 22069. The route then enters a final cutting as the ground level rises, with the end of Section 1 at CH 22800. This is at the north west extent of Sion Mills village, approximately 200m north of Primrose Park Road.

2.1.7 Parties to the Project

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

Organisation DRD Roads Service Western Mouchel Division

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

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

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

[email protected] [email protected]

Technical Approval Authority Designer’s Geotechnical Advisor

Organisation DRD Roads Service, Mouchel Headquarters

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

Northern Ireland, BT18 9JQ

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

Contact Mr Willie Kerr Mr David Towell

[email protected] [email protected]

GI Contractor Main Contractor

Organisation Glover Site Investigations Ltd BBM – Balfour Beatty, BAM, FP McCann Joint Venture

Address 8 Drumahiskey Road, c/o BAM Contractors Balnamore, Ballymoney, Co. Antrim, BT53 7QL Kill

Co. Kildare

Telephone 028 2766 2083 + 353 (0) 45 886400

Contact Mr John Cameron Mr William Diver

[email protected] [email protected]

2.1.8 Contracts

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

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

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

2.2 Scope and Objective of the Report

As discussed in section 2.1.4, a separate Ground Investigation Report will be submitted for each section of the scheme. This document refers to Section 1, from New Buildings to the South of Strabane.

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

Table 2-3: Report Volumes Volume Title

1 Introduction & General Principles

2 Findings of the investigation, Section 1A – New Buildings to Bready

CH 0 to CH 6550

3 Findings of the investigation, Section 1B – Bready Cutting

CH 6550 to CH 7260

4 Findings of the investigation, Section 1C – Bready to North of Burn Dennet

CH 7260 to CH 9870

5 Findings of the investigation, Section 1D – Burn Dennet to North of Glenmornan River

CH 9870 to CH 12340

6 Findings of the investigation, Section 1E – Foyle floodplain, including Glenmornan River

CH 12340 – CH 17040

7 Findings of the investigation, Section 1F – Mourne Crossing and Approaches

CH 17040 to CH 18680

8 Findings of the investigation, Section 1G – R. Finn Embankment to Urney Road

CH 18680 to CH 196550

9 Findings of the investigation, Section 1H – Cutting from Urney Road Past Strahans Road Quarry

CH 19550 to CH 20880

10 Findings of the investigation, Section 1I – At Grade Alluvial Section

CH 20880 to CH 21300

Volume Title

11 Findings of the investigation, Section 1J – Around Peacock Road Junction

CH 21300 to CH 22800

12 Environmental Testing Analysis

13 Risk Register

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

This volume, Volume 1, includes the following chapters

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 to use in the project)

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

Volumes 2 to 11 will include detailed Chapters 5 and 6 on the Ground Summary and the Ground Conditions and Material Properties in accordance with the Ground Investigation Report Template in HD22/08. Risks particular to the sub- section are detailed in Chapter 7 and this feeds in to the risk register for the whole section. © Mouchel 2010 20 718736-0600-R-006 Volume 1 of 13 - September 2010 A5 WTC - Section 1 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

Volumes 2 to 11 conclude with Chapter 8 detailing outline design recommendations for earthworks and foundations in the sub-section. These recommendations should be developed as part of the detailed design that will take place when the scheme has passed the public inquiry.

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

2.3 Geotechnical Category of Project

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

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

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

For Section 1 the following geotechnical issues are currently considered as Category 3. However it should be noted that the Geotechnical Classification should be reviewed as the scheme progresses and additional geotechnical issues could be added to this Category 3 list.

• Bready Rock Cutting

• Glenmornan River Bridge and Approach Embankments

• Embankments, Bridges and Flood Culverts on Soft Ground across Foyle Floodplain

• Mourne Crossing and Approach Embankments

2.4 Other Relevant Information

Not used.

3 Existing Information

A geotechnical Preliminary Sources Study (PSSR) for Section 1 was carried out by Mouchel in June 2009 (ref: 796036/0600/R/006A). The study reviewed the available published geological and geotechnical information for the Proposed Scheme.

This chapter provides a summary of the information that was collated and compiled during the preparation of the Section 1 PSSR and includes any new information received since the publication of the PSSR.

3.1 Sources of Information

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

Table 3-1: Sources of Information Information Source Data gathered Application of information Ordnance Survey Current OS mapping Man-made obstructions/voids/sources of contamination (July 2010) Historical Ordnance Survey of Man-made obstructions/voids/sources Northern Ireland Maps of contamination OSNI 1:10K Base map (2009) Historical mapping Former/present mining/quarrying and land-filling - Identification of geo- Digital historical mapping for hazards 1830’s, 1860’s & 1904, 1930’s (6 inch sheets), 1960’s and 2007 (1:10K sheets) Ortho Aerial photography Former/present mining/quarrying and (2009) 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 OSNI 1:10K Base map (2009) Digital Terrain Mapping Digital representation of the relief Geological Survey of 1:250 000 Geological Map of Solid geology along route corridor Northern Ireland Northern Ireland Solid Edition (2nd Edition, 1997)

Information Source Data gathered Application of information (GSNI) 1:250 000 Geological Map of Quaternary deposits along route Northern Ireland (Quaternary corridor Edition) Water Framework Directive The classification of bedrock and (2000/60/EC) Aquifer superficial deposits into aquifer Classification Scheme for categories Northern Ireland (2005) 1:250 000 Groundwater Identification of the vulnerability of Vulnerability Map of Northern groundwater to contamination - Aquifer Ireland recognition & groundwater conditions Groundwater Vulnerability An assessment of the vulnerability of screening methodology for groundwater within the uppermost Northern Ireland, aquifer Groundwater Management Programme, Commissioned Report CR/05/103N (2005) 1:250 000 Hydrogeological Hydrogeological risk assessment – Map of Northern Ireland Aquifer recognition & groundwater conditions Londonderry to Strabane Detailed Geological map 6inch Scale Geology Field Map Sheet 5 1907 - 1911

Strabane to Newtownstewart Identification of likely ground conditions 1:10K Geological field slip Mapping

Mineral Extraction Records Former/present mining/quarrying and land-filling - Identification of mineral extraction hazards Borehole Records – reports Historical information on geotechnical listed below & 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 Industrial Pollution Unit Identification of industrial operations, Environment Agency COMAH sites – Enforcements, (NIEA) prohibitions, prosecutions Contaminated Land Database Present/previous landfills & potentially contaminated sites Water Quality Management Sensitivity of ground/surface water for Unit drainage design, pollution incidents, consented industrial discharges, sewage discharges, designated groundwater extraction points.

Information Source Data gathered Application of information 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 Building Control Environmental Health Records of potential contaminating sites/landfills/fuel installations Londonderry, Planning Department Planning Applications, geotechnical & Strabane, Omagh contaminated land conditions and Dungannon District Councils Historical Ground Historical information on geotechnical Investigation Reports and groundwater conditions

The Department of Quarry and mineral database Identification of mineral extraction sites Finance and and hazards for Northern Ireland / Personnel, Central Republic of Ireland border area Procurement Directive Geological Survey of Land Slides in Ireland Location of historical land-slip areas Ireland

Mouchel Internal A5 WTC Preliminary Options Report Records

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

Information Source Data gathered Application of information 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 1 is provided in Table 3-2.

Table 3-2: Statutory Undertakers (Utilities) Authority Relevance to Scheme Phoenix Natural Gas Gas Service Locations Northern Ireland Electricity Electricity service locations British Telecom Telecommunication service locations Cable & Wireless Telecommunication service locations Telecommunications NI Water Water service locations Firmus Energy Gas Service Locations British Telecom Telecommunication service locations Cable & Wireless Telecommunication service locations Telecommunications Bytel Connections Telecommunication service locations Eircom UK Telecommunication service locations NI Water Water service locations

3.2 Previous Ground Investigations

The records from a number of previous site investigations undertaken by the Central Procurement Directorate (CPD), part of the Department of Finance and Personnel (DFPNI), has undertaken numerous ground investigations within the study area. The ground investigations were carried out for the various government sectors then known as Department of Finance (DOF) and Department of Health & Social Services (DHSS). Mouchel also hold records for a number of historical ground investigations obtained from the Geological Survey of Northern Ireland (GSNI) and included within the PSSR.

Details of all logs collected for the study area including material descriptions and any test results are hyperlinked within the exploratory hole location plan on Drawing 796036-0600-D-00062. The exploratory hole logs are displayed on the appropriate layer of the GIS model.

A summary of the data specific to the Proposed Scheme held by Mouchel and obtained from both CPD and GSNI for Section 1 (South of New Buildings - South of Strabane) is shown in the table below.

Table 3-3: Previous Geotechnical Studies Source of Information Document Reference/Year Produced by (click here for full reference details)

New Buildings Proposed Department of the Environment CPD Sewerage Scheme. SI 94032 (Water Executive) 1994 Realignment of A5, Victoria Department of the Environment CPD Road at Leckpatrick SI1396 (Roads Service) 1998 Strabane Bypass Phase 3 DFPNI (Roads Service) and CPD SI0602 2006 Owen Williams Strabane Bypass Mourne River Department of the Environment CPD Bridge SI87078 1987 - 88 (Roads Service) Customs Post Strabane CPD DFPNI SI6104 1961 N14/N13 Junction Donegal County Council (Manorcunningham) to Donegal County Council and Regional Roads Design Mott MacDonald Office Lifford/Strabane Scheme 2007 Strabane Acquisition – Orchard CPD DFPNI and Invest North Ireland Road Industrial Estate 2008

The findings of the information sources listed in this Chapter, including a summary of the ground conditions are discussed in Chapter 5 of this volume and in more detail in the individual sub-section volumes of this report.

4 Field and Laboratory Studies

4.1 Walkover Surveys

During preparation of the PSSR, a drive through survey was undertaken on the 3 and 4 March 2008 by Mouchel personnel to gain an initial familiarisation of the engineering study area and to identify the key geotechnical constraints.

Mouchel personnel then undertook a more detailed walkover survey of the engineering study area from the public highway from 18 March to 25 April 2008 inclusive. The walkover survey was carried out as a part of the geotechnical procedure to identify, inform and cross check from the published data as many as possible of the geological, geomorphological and man-made issues that might affect selection of a route and ultimately require a design solution. A Walkover Survey Report was produced (796036-0600-R-013).

Additional site survey work was undertaken in August 2008 during the data collection period to establish the status of the various gravel pits, quarries and landfill sites identified throughout the study area. This survey supplemented initial records obtained from the statutory agencies which did not make clear the current status of the sites, i.e. operational or disused, backfilled or open scars in landscape.

A preliminary visual survey of the Peat bogs identified throughout the study area was undertaken from the public highway on 28 July 2008 to confirm the type of Peat bog i.e. blanket (upland) Peat, inter-drumlin accumulations or raised (lowland) bog. A high level review of the stability of the Peat bogs was also undertaken.

Mouchel staff undertook a visual assessment of the key geotechnical constraints specific to the preferred route corridor on the 23 and 24 September 2008.

In addition to the above, during the supervision of the ground investigation fieldwork, engineers from Mouchel noted any salient observations.

Reference should be made to the PSSR and GIS model for a fuller description of the site. Extracts from the Walkover Report are available to view via hyperlinks within the GIS Model. The key findings, observations and photographs from the surveys are shown on the Drawings detailed in the table below.

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

4.2 Geomorphological/Geological Mapping

A scanline survey of an exposed rock face within the abandoned quarry near Bready (approximately CH 7200) was undertaken in order to inform the design of proposed rock cuttings through areas where the underlying bedrock was considered likely to be similar in nature. The results of this survey are discussed in detail in other volumes of this report for areas where rock cuttings are proposed.

4.3 Ground Investigation

Rationale for Fieldwork

A preliminary ground investigation was carried out during February and March 2009. The aim of this ground investigation was to obtain outline geotechnical data within the preferred corridor to allow a comparison between the route options and to assist in the decision making process of selecting the preferred route. This preliminary ground investigation also allowed ground investigation techniques to be trialled ahead of the main ground investigation.

The preferred route was then investigated by the main ground investigation with fieldworks taking place between September 2009 and April 2010. The purpose of the main ground investigation was to build on the findings of the PSSR and attain sufficient information in order that a design ground model could be created for the various design elements of the scheme. The ground investigation was designed to provide information on the following.

• A detailed knowledge of the stratigraphy of the route.

• The bearing capacity of soils to inform embankment and structural foundation design.

• The settlement characteristics of site soils to inform embankment and structural foundation design.

• The permeability of site soils to inform drainage design and embankment design.

• The reliable derivation of material parameters.

• Assessment of pavement foundation conditions.

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

• Nature and depth to rock, where rock excavation might be expected.

• The suitability of excavated site soils and rock for reuse in earthwork construction.

• The excavatability of the underlying rock.

• Nature and thickness of peat and soft alluvial soils where these have to be crossed.

• The groundwater regime beneath the site.

• The chemical characteristics of the soil in terms of aggressiveness to buried concrete, waste classification and potential risk to human health and/or environmental receptors.

In some instances the findings of the ground investigation were used (along with the findings of other design disciplines) to compare various potential route options in order to develop the route of the Proposed Scheme.

For the main ground investigation the spacing and type of exploratory hole was initially primarily determined by reviewing the geological mapping data together with information from exploratory holes formed during a preliminary phase of ground investigation. The fieldwork for the main ground investigation was carried out in three phases.

Phase 1 comprised an exploratory hole approximately every 1km and at the major structures to give a broad indication of what ground conditions could be expected along the route.

Phase 2 comprised holes around every 100m along the route to give a more comprehensive ground model. The method of exploratory hole formation, spacing and depth was reviewed and revised if necessary where Phase 1 holes encountered unexpected or problematic ground conditions. The Phase 2 ground investigation also targeted specific features identified in the PSSR such © Mouchel 2010 30 718736-0600-R-006 Volume 1 of 13 - September 2010 A5 WTC - Section 1 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

as areas of backfilling, areas of suspected Made Ground and potentially contaminated areas.

Phase 3 targeted the proposed positions of structures plus any areas where it was felt that the ground conditions encountered in Phase 1 and 2 required a greater level of investigation (generally where Peat or weak, variable Alluvial soils had been encountered).

4.3.1 Description of Fieldwork

Preliminary Ground Investigation

The preliminary ground investigation was designed by Mouchel; and carried out from 16 February to 20 March 2009. The locations of the exploratory hole positions were limited to land owned by Road Service.

The ground investigation works were undertaken by Soil Mechanics, a subsidiary of Environmental Services Group Limited (ESGL). The ground investigation works were carried out in accordance with BS 5930 (1999) and the Highways Agency Specification for Ground Investigation, as detailed in the Manual of Contract Documents for Highways Works (Volume 5, Section 3, Part 4) (1999).

The works comprised rotary boreholes, window sampling and cone penetration testing. Under sub-contract to Soil Mechanics, Lankelma performed the Cone Penetration Tests. Mouchel monitored the works full-time on site.

A summary of the exploratory hole details are presented below.

Table 4-2: Summary of Exploratory Hole Types

Exploratory Hole Type Number

Boreholes – rotary open hole with rotary coring 3 in rock

Window Sample Holes 65 at 53 locations

Cone Penetration Tests 21 at 19 locations

Standpipes were installed in BH02-N and BH04-N to depths of 31.6m and 30m respectively. In addition, standpipes were installed in fifteen window sample holes to a maximum depth of 6.0m.

Representative small disturbed samples were taken in window sample holes at approximate intervals of 0.5m to 1.0m and stored in airtight containers for identification, description and testing purposes. Classification testing was performed on the collected samples to determine moisture contents and Atterberg Limits. Occasional standard penetration tests were carried out in window sample holes.

The draft factual report by Soil Mechanics (Report ref Y9901, dated April 2009) contains the logs, in-situ field tests and results of laboratory testing. Logs are also hyperlinked within the exploratory hole location plan, Drawing 796036- 0600-D-00067 and are shown on the GIS model.

Main Ground Investigation

The main ground investigation was undertaken between 7th September 2009 and 16th April 2010. The works were carried out by Glover Site Investigations Limited (GSIL) who were contracted by the Client. Engineers from Mouchel designed, specified and supervised the works on behalf of the Client and instructed GSIL on the works to be undertaken

Exploratory holes were formed by a variety of techniques described in the following paragraphs and undertaken to the relevant standards outlined in the Factual Report. Lankelma undertook Cone Penetration Testing under sub- contract to GSIL.

The total figures for the main GI are summarised below.

Table 4-3: Summary of Exploratory Hole Types

Exploratory Hole Type Number

Phase 1

Cable Percussive Only 50

Cable Percussive with Boreholes 13 Rotary Follow-on

Rotary Only 5

Trial Pits 110

Cone Penetration Tests 67

Exploratory Hole Type Number

Phase 2

Cable Percussive Only 51

Cable Percussive with Boreholes 11 Rotary Follow-on

Rotary Only 5

Trial Pits 31

Window Sample Holes 16

Dynamic Probe Holes 13

Phase 3

Cable Percussive Only 86

Cable Percussive with Boreholes 21 Rotary Follow-on

Rotary Only 6

Trial Pits 37

The cable percussive boreholes were formed to depths of between 0.70m and 32.20m. Holes were terminated by the engineer when the design target depth was achieved or when the ground became too dense/stiff for the hole to be progressed further. In some instances, particularly holes formed in the Foyle floodplain, the holes could not be progressed to their design target depth due to artesian water conditions or ‘blowing sands’.

Rotary coring of underlying rock strata was either commenced from the base of a cable percussive hole to progress into the bedrock or in some instances, where bedrock was known to be close to the ground surface or data on the overlying superficial deposits was not required, commenced from the ground surface. Where the rotary was commenced from the ground surface, symmetrix cased drilling was undertaken in the superficial deposits with standard penetration testing at regular intervals.

Downhole optical and acoustic logging of eleven of the rotary holes was undertaken to provide an image of the wall of the borehole. This was

undertaken in holes formed in areas where cuttings are proposed through the bedrock. The optical probe comprises a 360° camera which is winched down the borehole to produce the image. The acoustic probe records the amplitude and travel time of a reflected acoustic signal of a focussed ultrasound beam to produce an image of the wall and was used when the groundwater in the borehole was too murky for the optical probe to produce a clear image.

Trial pits were formed using mechanical excavator to depths 0.60m and 4.60m. The pits were terminated either when the ground conditions became too hard to excavate or the maximum extension of the excavator was reached.

The window sample holes extended to depths of 1.0m and 5.0m bgl, terminating when the underlying ground became too stiff or dense to progress the hole further. Dynamic probing was undertaken adjacent to most of the window samples hole positions using super heavy equipment.

Groundwater was encountered in many of the exploratory during formation. Details of the water strikes are included on the relevant logs in the factual report and are summarised and discussed in the relevant Volumes of this report.

Exploratory hole location plans are included within the Factual Report and the hole locations are also plotted within the GIS model.

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

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

4.3.2 Soil Sampling

Undisturbed samples where obtained from cohesive soils encountered during cable percussive borehole formation, generally in the form of U100 samples with some piston samples where soils appropriate for this kind of sampling (soft clays) were encountered. Representative bulk and small disturbed samples of the various soils encountered were also taken at regular intervals in boreholes to allowing logging of the exploratory holes and to provide samples for geotechnical testing. Generally small disturbed (tub) samples were taken at the

same depth as each bulk sample together with samples of material recovered from Standard Penetration Tests.

During trial pitting, representative bulk and small disturbed samples of the various soils encountered were again taken for logging and testing purposes.

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

Rock cores were extracted from boreholes where rotary coring had been undertaken, with the cores transferred to core boxes for examination and logging.

Environmental samples comprising glass jars and veils were obtained in a selection of boreholes and trial pits. Such samples were obtained to give full spatial coverage of the site so that the chemical characteristics of the various site soils could be established. Such sampling was also undertaken where contaminated soils were suspected, either due to the nature of soils encountered or because information from the PSSR indicated they may be present. The environmental samples comprised 1 No. 1 kg tub sample and 1 No. 250g sample in an amber glass jar which was used in order to preserve any volatile organic chemicals. Prior to testing the samples were stored at between 0°C and 4°C.

4.3.3 Borehole Installations

Groundwater monitoring instrumentation was installed in many of the boreholes comprising either 50mm slotted standpipes or 19mm piezometer standpipes. The location and type of installations were chosen to allow a model of the groundwater to be established with slotted standpipes generally installed to establish the standing groundwater levels and piezometers to target specific water strikes encountered during hole formation. The installation details are included in the Factual Report.

Groundwater monitoring at each installation was undertaken on a weekly basis for a month after installation. Further readings were then taken on a weekly or monthly basis over the duration of the fieldwork period dependant on the groundwater condition recorded. Further groundwater monitoring will be undertaken on a monthly basis for those holes where further groundwater information is required to inform the design.

Bungs were added to two of the installations to allow gas monitoring, with monitoring subsequently being undertaken on three occasions. The gas

monitoring was undertaken where materials considered to represent potential sources of hazardous ground gases were encountered in areas where the highway design included features in which such gases may accumulate.

The details and findings from the groundwater and gas monitoring are discussed further in the relevant subsection volumes of this Report. 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 11.

4.3.4 Results of In-Situ Tests

Standard penetration testing was undertaken at regular intervals during hole formation to give an indication of the underlying strength or relative density of the underlying soils. 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. These ‘N’-values are uncorrected, the SPT calibration certificates are included in the Factual Report.

Permeability testing (falling or rising head) was undertaken in 17 of the boreholes to provide information on the permeability of the various site soils beneath the route.

Dynamic probing was undertaken adjacent to thirteen of the window sample hole positions. Plots of the number of blows per 100mm against depth are included in the Factual Report.

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

The cone penetration tests (CPT) were undertaken to depths of 0.33m to 35.05m. This technique was largely used in areas where soft alluvial soils were suspected or known to be present, as it is considered that this technique is most suitable for such soils. Twenty-three dissipation tests were undertaken during progression of various the CPT to give information on the rate of dissipation of pore pressures within the various soil horizons.

The results of the in-situ testing carried out during the ground investigation are detailed on the appropriate logs and appendices contained in the Factual Report. The findings of the in-situ testing are presented graphically and discussed in more detail within the relevant subsection volumes of this report.

4.3.5 Ground Investigation Factual Report

The preliminary Ground Investigation is detailed in a draft factual report produced by Soil Mechanics, Report No. Y9901, dated April 2009. This contains the logs, in-situ field results and results of laboratory testing.

The main ground investigation is detailed in a factual report produced by GSIL titled A5 Western Transport Corridor Section 1; New Buildings to south of Strabane; Ground Investigation, Report No 09-0900, dated June 2010. This comprises 10 Volumes and should be referred to in conjunction with this report.

Logs from both investigations are also hyperlinked within the exploratory hole location plan, Drawing 796036-0600-D-00095.

4.4 Drainage Studies

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

4.5 Geophysical Survey

Not Used.

4.6 Pile Tests

Not Used.

4.7 Other Field Work

Reference to the Environmental Statement (Ref. 718736-3000-R-008) should be made for detailed analysis of the findings of environmental surveys and assessments.

4.8 Laboratory Investigation

4.8.1 Description of Tests

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

Classification tests undertaken include; moisture content, Atterberg limits, particle size distribution, bulk density and particle density. Compaction tests undertaken included; determination of dry density/moisture content relationship (2.5 + 4.5 kg), moisture condition value (single point and moisture content relationship) and re-compacted California Bearing Ratio (CBR) tests.

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

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

Chemical tests undertaken included; pH, water soluble sulphate and organic matter content. The results of testing for contamination and waste acceptance criteria are discussed in Volume 12 of this report.

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

Classification/Compaction

Moisture Content BS1377: Part 2: 1990; Clause 3 854

Liquid / plastic limits BS1377: Part 2: 1990 697

Bulk Density BS 1377: Part 2: 1990 8

543 (sieve only) Particle Size Distribution BS1377: Part 2: 1990; Clause 9 704(sieve and sedimentation)

Geotechnical Test Test Method No. Tests Undertaken

Determination of dry density/moisture content BS1377: Part 4: 1990 42 relationship (2.5kg hammer)

Determination of dry BS1377: Part 4: 1990 8 density/moisture content relationship (4.5kg rammer)

Recompacted California BS1377: Part 4: 1990; Clause 7.4 47 Bearing Ratio

MCV (single point) BS1377: Part 4: 1990 31

Los Angeles Abrasion BS EN 1097-2: 1998 12

Strength / Consolidation

Undrained triaxial (total) 167 BS1377: Part 7: 1990 strength (multistage)

Undrained triaxial (total) BS 1377: Part 7: 1990 0 strength (remoulded)

Shear Box (effective 2 BS1377: Part 7: 1990; Method 4 strength)

Consolidated undrained 13 triaxial (effective) BS1377: Part 7: 1990; Method 4 strength

Point Load Index ISRM 322

Unconfined ISRM 34 Compressive Strength

BS1377: Part 5: 1990 Clause 3 141 1-D oedometer BS1377: Part 6: 1990 Clause 3 3 (Rowe Cell)

Chemical (tests on soils and groundwater)

pH, water soluble BRE 279 99 sulphate, Magnesium, Chloride TRL Report 447

Organic Matter Content BS 1377: Part 3: 1990 188

4.8.2 Copies of Test Results

Reference should be made to the Factual Report which contains all the results of the testing undertaken. The test results are also contained within the AGS data. This information is available with the GIS model.

5 Ground Summary

Provided in this chapter of the report is a general description of the ground summary. More detailed ground summaries are provided within Volumes 2 to 11 of this report and for more information regarding the site refer to the PSSR (Ref: 796036/0600/R/005A).

5.1 Geography

Section 1 of the Proposed Scheme is situated in the west of Northern Ireland and extends from New Buildings in the north (CH 0) to the south of Strabane at Sion Mills (CH 22800). In general the route of the Proposed Scheme is located to the west of the existing A5 throughout Section 1, except for one part of the route. Section 1 starts in County Londonderry passing into County Tyrone just north of Magheramason.

Section 1 of the Proposed Scheme is located near a number of towns and villages. The route starts in the village of New Buildings which is located approximately 4km south west of Londonderry on the east bank of the River Foyle. It passes to the west of the small village of Magheramason (CH 3500), the east of Bready village (CH 7200) then to the west of the hamlet of Cloghcor (CH 11000) and village of Ballymagorry (CH 13500) .

From approximate CH 15500 to CH 21000 the route by-passes the town of Strabane. Strabane is the largest residential, administrative and commercial centre settlement in the vicinity of Section 1. The existing A5 runs generally around the western and southern boundaries of the town, while the route runs through agricultural land further west and south beyond the town outskirts.

Section 1 ends to the north west of Sion Mills, approximately 200m north of Primrose Park Road. The existing A5 runs through the centre of Sion Mills, and acts as a bottle neck for the traffic due to speed limitations.

The land across which the new alignment will cross is generally farmland used for arable and grazing purposes.

Recognised ecological and nature conservation interests comprise the following.

• The River Foyle and Tributaries Special Area of Conservation (SAC) and Area of Special Scientific Interest (ASSI) (this includes the River Finn and River Mourne) © Mouchel 2010 41 718736-0600-R-006 Volume 1 of 13 - September 2010 A5 WTC - Section 1 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

• McKean’s Moss ASSI

The Foyle Valley Deglacial Complex is also designated as a Habitas earth science conservation sites, though it is not affected by the Proposed Scheme.

Where the proposed road corridor passes to the west of Strabane and along the immediate eastern margin of the River Finn, the principal environmental interests comprise the residential community that frames the urban edge of the town and the ecologically important River Finn.

5.2 Topography

In general the topography along Section 1 is governed by the natural limits of the floodplains of the River Foyle and its tributaries and the higher ground of the Sperrin Mountains to the east. It is a large-scale and imposing landscape in which the wide valley floor flanking the river channel is framed by the prominent profile of the Sperrin Mountains. A series of foothills form the transition from the high valley perimeter to the wide valley floor.

A relief map of the topography is available on the GIS model and is shown on Drawing Number 796036-0600-D-00068. Elevations can also be observed on the GIS model with 10m contours provided. The steepness of the terrain is also available on GIS and Drawing Number 796036-0600-D-00069

Between New Buildings and Strabane the proposed scheme is located within the broad valley of the River Foyle.

Along the northern extent of the route from New Buildings to Bready the topography comprises gently undulating ground with ground levels generally between 5m OD and 20m OD.

At Bready (CH 7000) the route passes in a deep cutting through the western extent of Gortmonly Hill, a foothill of the Sperrins. Ground level at the top of this cutting is approximately 80m OD.

Ground level then falls towards the River Foyle floodplain just north of the Burn Dennet at approximately CH 10000.

From this point to the River Mourne the route continues along the River Foyle floodplain with ground levels generally less than 5m OD. The route passes across localised sandy ridges within the floodplain (typically 10m OD) and between CH 11320 and CH 12340 the route is on a terrace of slightly higher

ground (approximately 15m OD) above and east of McKeans Moss, at the edge of the floodplain.

South of the River Mourne the route continues to CH 19500 along the bank of the River Finn where the ground level is less than 10m OD. As the route turns southwards and away from the River at Urney Road, the ground then generally rises at Carricklee Hill and Orchard Hill. The topography is then more undulating with ground levels between 10m OD and 40m OD between here and Sion Mills.

5.3 Historical Development

Historical records date back to 1830 with historical maps and aerial photographs. Historical development is discussed in detail in the PSSR and the individual sub-section volumes.

The general study area remains largely agricultural with some residential and industrial development associated with the urban areas.

The key development for Section 1 is associated with the following features.

• Strabane Canal was present prior to 1830. There were a number of developments associated with the canal in Strabane town centre. The canal is known to have become disused around the 1960s.

• Strabane was shown as a small town by 1830. Between 1904 and 1930 there was an area of development of Strabane town to the south of the River Mourne. Significant residential, industrial and retail development took place around Strabane between 1960 and the present day.

• The villages along the route have developed over the years with the main residential development between 1960 and the present date.

• Sewage works were developed close to (but not on) the preferred route alignment at Magheramason and the northwest edge of Strabane.

• It is understood that the Great Northern Railway was constructed in the mid 1800s. This ran to the west of Strabane, with two bridges across the River Mourne and included a branch for the Donegal Railway. By 1960 the railway had been abandoned. The route passes over the old railway station immediately to the northeast of the existing A5/A38 junction. The route follows the line of the Donegal Railway alongside the River Finn.

• By 1830 a road was present along much of the length of the existing A5 road. This was except for a section by Ballymagorry and the length around Strabane.

• Construction of a new section of the existing A5 took place along the Great Northern Railway line in the south of Strabane in the late 1990s (known as the Great Northern Link Road). A further section of the existing A5 (approx. 1.8km at Ballymagorry) was constructed along the railway branch line to the north of Strabane.

• Construction of the current A5 Mourne Bridge took place in the early 1990s.

• By 1960 a quarry was shown at CH 20500.

• A landfill site was developed adjacent to the Canal at the current site of Strabane Cricket Ground and the route crosses this at CH 17200. This was disused before 1973.

• A second landfill site was operated by Strabane District Council adjacent to Urney Rd & the River Finn until closing around 2007. It still operates in 2010 as a waste reception site.

5.4 Mining and Quarrying

Quarrying is widespread in the region however many quarries have now been backfilled or are disused.

The key quarrying locations affecting the Proposed Scheme are a disused quarry adjacent to the proposed Bready cutting (CH 7200) and a disused flooded quarry located adjacent to the route to the south west of Strabane at Strahans Road (CH 20500)

Sites with active sand and gravel extraction are present in the area and there is a number of backfilled sand or gravel pits in the vicinity of, but not affecting, the Proposed Scheme.

More detail is given in the sub-section specific volumes with information on more minor quarry and sand and gravel pit locations discussed.

A disused lead mine is located east of Strabane on the banks of the River Mourne in the vicinity of Milltown, where two short mine adits are located, though these do not affect the Proposed Scheme.

The GSNI has confirmed that there is no oil and gas exploration within the area. No mineral (coal or metal) workings are present along the route, though metal veins are shown on the GSNI maps throughout the district.

5.5 Hydrology

There are a number of significant watercourses associated with the route of the Proposed Scheme. The route from New Buildings to Strabane is approximately parallel to the course of the River Foyle, being up to 2km from the river. At Strabane the route crosses the River Mourne and runs adjacent to a section of the River Finn. These rivers converge to become the River Foyle. The route crosses the Burn Dennet and associated valley and the Glenmornan River, which are both tributaries of the River Foyle. The route also crosses a number of smaller watercourses including New Buildings stream, Bready stream and Ballymagorry Burn. Along with those listed there are numerous minor watercourses and drainage ditches, in some cases unnamed, that the route intersects. For more information on these watercourses refer to the sub-section GIR Volumes.

5.6 Geology

This section gives a brief generalised overview of the geology across the whole of Section 1. A more detailed discussion of localised geology and ground conditions is presented in volumes 2 to 11 of this report.

5.6.1 Superficial Geology

Topsoil and Made Ground

Topsoil was encountered in the majority of the holes formed in the rural parts of the site, generally 200mm to 300mm in thickness.

Occasional areas of Made Ground were encountered along the whole of the route. These deposits were generally less than 1.00m thick and comprised reworked natural soils. The most significant areas were encountered around Strabane, particularly between CH 19000 and CH 19500 where Made Ground was encountered extending to depths of 2.00m to 4.00m. It comprised sandy gravel with various artificial inclusions and appears to be associated with attempts to level/raise areas of land adjoining the River Finn.

Alluvium

Large sections of the central part of Section 1, between CH 10400 and CH 19500, are underlain by drift deposits comprising alluvium associated with the floodplain of the River Foyle and its tributaries. The ground investigation found the alluvium generally comprises soft organic silts and clays extending to depths of 5m to 15m bgl. Occasional pockets of peat were encountered within the alluvium, generally being less that 1m thick. The greatest depths of alluvium were encountered in proximity to three major water courses which cross the route, namely the Burn Dennet, Glenmornan River and the River Mourne. Around the Glenmornan and Mourne the alluvium extended to depths of in excess of 30m with interbedded layers of silty sand and sandy silt underlying the organic clay/silt.

Localised areas of alluvium associated with minor watercourses were also encountered in other discrete areas of Section 1. This generally comprised soft to firm clay, extending to depths of less than 2.00m.

Lake Alluvium

An area of Lake Alluvium (lacustrine deposits) is depicted beneath the route between CH 20900 and CH 21300 at Bog Rd / Knockroe Rd. The ground investigation found these deposits generally comprised soft silty clay and extended to depths of up to 9m.

Glacial Deposits

The geological mapping for the area shows the northern part, between CH 0 and CH 10000, and the southern part, between CH 19500 and CH 22800 of Section 1 to be underlain entirely by drift comprising glacial deposits. Glacial deposits underlie much of the alluvium in the Foyle floodplain which dominates the centre part of the route. It is also present at the surface in some areas of the central part of the route where the alluvium in absent.

From CH 0 to CH 8600 these deposits are depicted as glacial till. This glacial till tended to be predominantly granular and generally comprised medium dense clayey/silty sand or gravel interbedded with horizons of firm to stiff sandy clay or silt. It generally extended to depths of 3m to 10m bgl, with bedrock near-surface or out-cropping in some places.

From CH 8600 to CH 104000 the glacial deposits are depicted as glaciofluvial sand and gravel. These generally comprised medium dense, becoming dense at depth, clayey/silty gravelly sand or sandy gravel with occasionally interbedded cohesive layers. Between CH 10400 and CH 19500, where the glaciofluvial deposits are interspersed/underlie the alluvium of the Foyle Floodplain, the glaciofluvial Deposits are generally coarser in nature, comprising medium dense to dense sandy gravel and extending to depths of 10m to in excess of 30m.

The southern part of Section 1, from CH 19500 onward (South of the River Mourne), is depicted as being underlain by glacial moraine deposits from CH 19500 to CH 19700, glaciofluvial sand and gravel between CH 21800 to CH 22200 and glacial till in all other areas (also underlying the Lake Deposits). The ground investigation showed very little difference in the ground conditions between the areas described as till and moraine. These deposits tended to extend to depths of 2.00m to 10.00m and were similar in nature to those underlying the north of the section other than there tended to be a greater percentage of cohesive material with in the areas of till and boulders were often encountered toward the base of the horizon.

5.6.2 Bedrock Geology

Published geological data shows the solid geology underlying Section 1 comprises the Ballykelly Formation from CH 0 to CH 2800 and the Claudy Formation beneath the rest of the site. Both belong to the Dalradian age Souhtern Highland Group and form the north limb of the Sperrins Nappe. The Ballykelly formation is described as mixed psammite (metamorphosed sandstone) and pelite (metamorphosed mudstone) and the Claudy formation is described as psammite units up to 1m thick alternating phyllitic semipelite (phyllite being metamorphosed mudstone with a well defined cleavage / parting eg shale, slate). The bedrock is depicted as outcropping beneath discrete sections of the route between CH 4350 and CH 7350. The ground investigation generally encountered bedrock at variable depths of between 2m and 20m, however the bedrock was often not encountered in the holes formed along the central part of the route where the base of drift deposits could not be proved beneath the Foyle floodplain (depth to bedrock in excess of 30m). The bedrock encountered in the ground investigation was generally described as interbedded grey psammite, pelite and phyllite. Around CH 20500 (south of Strabane), metamorphosed limestone and quartzite was also encountered. In all cases only the top of the mapped geological formation was encountered and in no instances were underlying formations encountered in exploratory holes.

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);

• 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 (6 bedrock and 2 superficial) based on geological strata type, relative resource productivity (high/moderate/limited/poor) and flow type (fracture/intergranular). The classifications are as follows:

− High productivity bedrock aquifer with fracture flow: Bh(f);

− High productivity bedrock aquifer with fracture/intergranular flow: Bh(I- f);

− High productivity bedrock aquifer with fracture flow with a karstic element: Bh(f-k);

− Moderate productivity bedrock aquifer with fracture flow: Bm(f);

− Limited productivity bedrock aquifer with fracture flow: Bl(f);

− Poor productivity bedrock aquifer with fracture flow: Bp(f);

− High productivity superficial aquifer with intergranular flow: Sh(I);

− Moderate productivity superficial aquifer with intergranular flow: Bm(i).

The groundwater vulnerability classification comprises classes 1 to 5, with 1 being the lowest vulnerability and 5 being the highest vulnerability, and 5 sub- classifications (4a — sand and gravel cover non-aquifer, 4b — moderate permeability cover, 4c — low permeability cover, 4d — thin soil over bedrock,

4e — where superficial aquifers are present) 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.

Aquifer Classification

The fractured Precambrian bedrock aquifers underlying Section 1 are classified as fracture flow of limited productivity BI(f). Moderate yields are unusual from such aquifers and lower yields are more common. Regional flow is limited and it is mainly shallow, local flow.

The superficial glaciofluvial and alluvial deposits act as a superficial aquifer. A superficial aquifer of glaciofluvial sands and gravels which support intergranular flow blankets much of the area

A number of superficial aquifer deposits are recognised beneath Section 1. These are the glacial sands and gravels and granular alluvial deposits associated with the River Foyle floodplain, which are generally present between Cloghcor and Urney Road. These glacial sands and gravels and overlying

granular alluvial deposits are classified as a superficial aquifer supporting intergranular flow.

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

Groundwater Vulnerability

Groundwater vulnerability along Section 1 is generally indicated to be Class 4, high vulnerability. This is split into Class 4e (where superficial aquifers are present) for the central part of Section 1 and Class 4a (sand and gravel cover non-aquifer) for the northern and southern part of Section 1.

There are localised areas with other vulnerability classifications apply.

− Where the superficial cover is thin or absent, in the vicinity of New Buildings and Bready, the vulnerability is Class 5, highest vulnerability.

− The presence of the isolated area of raised peat bog overlying the alluvial and glaciofluvial deposits between Leckpatrick and Ballymagorry reduce the vulnerability rating of the fractured bedrock aquifer in this area to 2, moderate.

− There is a small area with Class 3 where there is Lake Alluvium present between Bog Road and Knockroe Road.

5.8 Geomorphology

Geomorphological features that are relevant to the scheme are discussed in the individual sub-section volumes.

6 Ground Conditions and Material Properties

6.1 Introduction

The route has been split into sub sections based on geography and geological/geotechnical similar areas. Ground conditions and material properties for each of these sub sections will be discussed in detail in Volumes 2 to 11.

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 internal advice memo, February 2010).

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

• The results of geotechnical laboratory testing

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

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

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

6.1.2 Correlations used for use with both Cohesive and Granular Material

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

6.1.2.1 Coefficient of Horizontal Consolidation (ch )

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

Figure 6-1: ch values derived from t50 values (after Robertson et al 1992)

6.1.2.2 Coefficient of Vertical Consolidation (cv )

The ratio of ch/cv is normally between 1 and 2 (Ref Craig, 2004).

Bergado, 1994 gives the ratio as ch = (kh/kv) cv with the kh/kv ratio varying with the fabric of the soil in accordance with the following table.

Table 6-1: Range of Field values of kh / kv 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 N100 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 N100 to SPT N values

while others sum groups of three consecutive N100 values to obtain an equivalent N Value, i.e:

N = N100 + N100 + N100 Equation 6-1

The relationship is only linear between 5≤N100≤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 = 0.15M0.96 Equation 6-2

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

6.1.2.4 Permeability (k)

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

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

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

6.1.2.5 Young’s Modulus (E)

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

E = 17.6(CBR)0.64 MN/m2 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 = 300cu 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 (φ' ) 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 (φ' )

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 φ' 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 (qc) (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 qc + 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 Table 6-4 (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

10 φ' residual Angle of Shearing Resistance (Degrees) Resistance Shearing Angle of

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

0 0 102030405060708090100110120 Plasticity Index (%)

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

6.1.4.2 Undrained Shear Strength, cu

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 = f1N (kN/m ) Equation 6-11

Where f1 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 cu 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+0.0037Ip).σ’v Equation 6-13

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

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

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

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

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

Log cu = 0.2 + 2.0IL Equation 6-15 Undrained shear strength has also been calculated from the results of the cone penetration testing using:

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

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

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

6.1.4.3 Co-efficient of Volume Compressibility (mv)

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

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

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

2 mv = 1/(f2N) (m /MN) Equation 6-17

where f2 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 mv using the following relationship:

E’ = 1/mv Equation 6-18 Using the Stroud correlation this can therefore be related to N value using the following equation.

2 E’ = f2N (MN/m ) Equation 6-19

6.1.4.5 Compression Indices

Although mv 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 (Cc)

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 = (e0- e1)/log(σ’1/ σ’0) Equation 6-20 Gregory and Bell, 1991, proposed the following relationship specifically for Belfast tills which are likely to analogous in properties to tills in the area of the A5. This is similar to an earlier correlation proposed by Skempton, 1944.

Cc = 0.004(LL-5) Equation 6-21

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

Cc = ½ Ip.Gs Equation 6-22

Where Ip = plasticity index and Gs = specific gravity.

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

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

Cc = 0.0065.w for bog peats Equation 6-23

Cc = 0.008.w for fen peats Equation 6-24 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 (Cr) or swelling index (Cs) 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.

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

Cr = 0.0015LL Equation 6-25 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

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

Cα = (e0- e1)/log(t1/ t0) Equation 6-26 (after Carter and Bentley, 1991)

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

Cα = 0.00018.w Equation 6-27

6.1.4.8 Pre-consolidation Pressure (pc’)

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 oedometer 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+0.0037Ip) Equation 6-28 (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 and effective overburden stress with the following correlation:

1.25 OCR = [(cu/σ’v)/0.25] Equation 6-29 (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/(mvγwcu) Equation 6-30

Where k= co-efficient of permeability (m/s) and γw is the unit weight of water which= 9.81kN/m3.

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

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

6.1.4.11 Californian Bearing Ratio (CBR)

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

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

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

Table 6-7: Equilibrium Subgrade CBR Estimation

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

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

CBR = cu/23 Equation 6-31 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 6-32 (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 = CIs Equation 6-33 (from Farmer, 1983)

Where σcf = UCS, Is = 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 Is 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 6-34 (after Barton, 1971)

Where:

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

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

JRC can be determined from Figure 6-9.

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

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

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

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

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

cut, height of slope etc. The following formula calculates Erm.

1− D / 2 E = E (0.02 + ) Equation 6-35 rm i 1+ e ((60+15D−GSI ) /11)

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

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

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

calculates Erm. 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.Mrquc Equation 6-36

Where j = rock mass factor; Mr = modular ratio and quc = unconfined compressive strength.

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

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

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

6.1.6 Conclusions

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

7 Geotechnical Risk

Refer to Volume 13.

8 Basic Design Philosophy and Methodology

8.1 Introduction

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

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

The designs have been refined as necessary to suit site specific conditions and were modified as described are described in the appropriate sections in Volumes 2 to 11.

8.1.1 Earthworks Definitions

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

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

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

Side long ground is when one side is in cut and the other on embankment. The centreline long section will not show the full earthwork heights and cross sections are generally required to clarify the earthworks profile. Because of groundwater issues, and changing the slope loading, these can be particularly sensitive to slope stability, often requiring a shallower slope.

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

8.1.2 Groundwater

The ground water 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 (cu) for short term conditions

• 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/m2 has modelled throughout on the footprint of the road with a surcharge of 10kN/m2 on verges and above the slopes to model agricultural traffic and the like.

Unless otherwise stated a c’ of 1kN/m2 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 cr’ of 0. In clay slopes a value of φ' = 30° was used and in sand and gravel, φ' = 36°.

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

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 mid height, of at least 2m wide to maintain stability. The berm should slope outward 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 1930s and the 1970s the majority of rock slopes were constructed with slope angles of 3v or 4v:1h without much regard to the local geology or discontinuities. Slopes of these angles, which did not have some form of inbuilt stability protection, invariably required later remediation and maintenance during their design life.

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

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

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

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

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

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

• Boulder trenches at the toe of the slope to catch falling debris. For initial design purposes this it is recommended that this is 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 drift 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 <4m high. The safe angle of slope for the drift deposits will also have to be determined.

• If a rock slope is of a low height consideration will be given as to whether to treat it as a soil slope with a slope angle of 1v:2.5h as this may require less land take than a slope incorporating boulder trenches. For example for a rock face that is stable at a slope of 1v:1h, less land take is required up to a height of 4m to construct the slope at an angle of 1v:2.5h without a boulder trench rather than construct it at 1v:1h with © Mouchel 2010 78 718736-0600-R-006 Volume 1 of 13 - September 2010 A5 WTC - Section 1 Ground Investigation Report - Volume 1 Introduction Job_Name4and General Principles

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 β D 30

W 4

1.25 Key 20 D

3 W Slope height, H (m)

10 2

1.0

1 0 90 80 70 60 50 40

Slope angle, β (degree )

Figure 8-2: Rock Slope Land Requirements

Cutting land take requirement

12 w idth of boulder 10 trench 8 w idth of boulder slope ht slope 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 1020304050 slope width

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 terms 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 20kN/m2 has been modelled on the carriageways with a 10kN/m2 on the verges.

The required Factor of Safety is 1.3.

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

Materials

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

determined by the use of mv and cc values derived from oedometer tests and the correlations given in Chapter 6.

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

For stiff over consolidated clays:

Immediate settlement = ρi = 0.5 to 0.6 ρoed

Consolidation settlement = ρc= 0.5 to 0.4ρoed

Final settlement = ρoed

Where ρoed = settlement as calculated from oedometer tests.

For soft normally consolidated clays:

Immediate settlement = 0.1ρoed

Consolidation settlement = ρoed

Final settlement = 1.1ρoed

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 µg from the following table.

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

Type of Clay µg

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

Normally consolidated clays 0.7 - 1.0

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

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

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

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

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

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

ss = Ho.cα.log(tf /to) Equation 8-1 Where:

Ho = Thickness of compressible material strata following primary consolidation.

cα = Secondary compression index

tf = Time at finish (design life)

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

Embankments over Poor Ground Conditions

Excavation and Replacement

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

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

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

A typical section is shown in Figure 8-3.

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

W=3D Embankment with 1:2.5 side slopes

D Buried Embankment with 1:2 side slopes Soft ground

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

Experience at Cabragh on the A4 between Dungannon & Ballygawley (Aug 2010) has indicated that in many cases, deep inter-drumlin fen deposits, consist of less than 3m of 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 into the rock. 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/m2. 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 weak soils. Construction of temporary berms at the base of the slopes and the use of basal geotextile reinforcement may prevent bearing capacity failure on weaker soils and permit higher lifts.

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

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

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

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

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

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

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

Flood Protection for Embankments

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

8.2.3 Re-use of Materials

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

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

If the undrained shear strength is too low severe rutting and deformation may occur when fill is being placed. A shear strength of 30-50kN/m2 (Ref Highways Agency, 1991) is therefore typically used as lower bound strength for re-use.

In addition, for most types of clay fill, under compaction may occur if shear strengths are too high. HA44/91 gives a typical upper bound figure of 150 to 200kN/m2. Class 2C, Stony Cohesive Material, however, does not have an upper bound figure as the clast content of the material aids the breakdown of large blocks under compaction. It is likely that the majority of the cohesive glacial till that will be excavated as part of the works will fall into this category.

The re-use potential on the scheme has been analysed by review of natural moisture contents (nmc), optimum moisture contents (omc) from compaction

tests, undrained shear strength, moisture condition values (MCVs) and Californian Bearing Ratio (CBR) tests.

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

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

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

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

As a guide any soil with a moisture content leading to a CBR <2%, a cu of <50 kN/m2, a nmc > optimum moisture content +2%, or a soil with a MCV<7 is probably too wet for reuse for general earthworks fill. It may however, be suitable as Class 4 landscape fill.

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

Rippability of Rock

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

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

An additional method used is that given in Trenter, 2001 which includes a diggability index ranking (Figure 8-5 & Table 8-3) which is used as a basis for a

Diggability Classification for Excavators, as shown in Table 8-4. Using this index a suggested type of excavator can be determined.

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

Point Load Index 0.1 0.3 1.0 3.010.0 30.0 6.0 6.0 216 Blasting or Hydraulic Breaking Very 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 H R pi Medium a ip n r p g d i R n

g l=b=w) ( Assumes ip 0.2 p 0.2 0.08 in g E - Fracture Spacing Index (m) Index Spacing Fracture 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 Size (m3) Size Block Equivalent 0.02 0.02 2 6 20 60200 600 Approx. UCS (MPa)

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

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

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

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

8.3 Highway Structures

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

Settlement has been calculated as described above.

8.4 Strengthened Earthworks

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

8.5 Drainage

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

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

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

• Ditches at the toe of embankments to control run off and increase the stability of the embankment. The ditches should be placed at least 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 tills in times of adverse weather.

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

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

8.6 Pavement Design, Subgrade and Capping

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

IAN 73/06 defines four foundation classes based on the Foundation Surface Modulus Value1.

• 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 Modulus2 which is determined using the lowest value of the long term and short term CBR.

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

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

CBR values determined using laboratory tests are generally short term CBR values. Long term, equilibrium values for cohesive materials have been determined using Plasticity Indices. Table 5.1 of IAN 73/06 tabulates estimated CBR values from PI data and grading results however it is recommended that the table from the original issue of IAN 73/06 is used to determine CBR values (reproduced as Table 6-7) as this brings in variations in water table and construction conditions. For preliminary design purposes average construction conditions have been assessed with variations in water table altered to suit the particular site conditions. A thick construction3 has been assumed for preliminary design.

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

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

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

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

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

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

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 150mm is used to even out hard spots, and to ensure that the pavement construction thickness is uniform.

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

8.7 Contaminated Land

A discussion about any contaminated land is contained in Volume 12 of this report.

8.8 Ground Treatment Including Treatment of any Underground Voids etc

8.8.1 Soft Spots

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

8.8.2 Water Courses

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

8.9 Specification Appendices

Not included in outline design.

8.10 Instrumentation and Monitoring

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

Principal Symbols

Table 8-5: Principal Symbols Symbols Name Units

CBR Californian Bearing Ratio %

2 ch Co-efficient of Horizontal Consolidation m /yr

2 cv Co-efficient of Vertical Consolidation m /yr

Cc Compression Index

Cs/ Cc Swelling/re-compression Index

Cα Coefficient of secondary compression

cu Undrained (total) shear strength parameter kPa or kN/m2

c’ Drained (effective stress) shear strength kPa or parameter kN/m2

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/m2

σ'v Effective Vertical Stress (pressure) kPa or kN/m2

σ'c Pre consolidation pressure kPa or kN/m2

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 7th , 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, 2nd 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 3rd 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, 2nd edition, John Wiley and Sons

6.28. Tomlinson, M.J., 2001, Foundation Design and Construction, 7th 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. Bieniawski, Z.T. (1976) Rock Mass Classifications in Rock Engineering, Proc. Symp. Expl. Rock Eng., Johannesburg, Balkema, Cape Town, Vol. 1 pp. 97- 106

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

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

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

Appendix A GIS Navigation Guide

Introduction

To aid with the management of the large volume of information gathered and assessment of parameters, drawings referenced 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 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.

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.

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

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