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REPORT

Earthquake Commission Darfield Earthquake Recovery Geotechnical Factual Report Avonside

Darfield Earthquake Recovery Geotechnical Factual Report Avonside T&T Ref. REP-AVS-FAC

Earthquake Commission February 2011

REPORT

Report prepared for:

EARTHQUAKE COMMISSION

Report prepared by:

TONKIN & TAYLOR LTD

Distribution:

EARTHQUAKE COMMISSION 3 copies

TONKIN & TAYLOR LTD (FILE) 1 copy

February 2011

T&T Ref: REP-AVS-FAC




Table of contents

1 Introduction 1

2 Project background 1

3 Site description 2 3.1 General 2 3.2 Regional geology 2

4 Geotechnical investigations 2 4.1 General 2 4.2 Cone penetration testing (CPT) 2 4.3 Machine boreholes 4 4.4 Geophysical testing 5

5 Groundwater observations 5

6 Laboratory testing 5

7 Environment Canterbury information 5

8 References 6

Appendix A: Investigation Location Plans

Appendix B: Cone Penetration Testing

Appendix C: Borehole Logs

Appendix D: Borehole Core Photographs

Appendix E: Geophysical Testing

Appendix F: Laboratory Testing

Appendix G: Environment Canterbury Borehole

1



1 Introduction

The Earthquake Commission (EQC) engaged Tonkin & Taylor (T&T) to undertake site investigations around selected suburbs of Canterbury following the Darfield Earthquake sequence that started on 4 September 2010. These site investigations comprise:

a) Cone penetration testing b) Machine boreholes c) Geophysical testing d) Groundwater observations e) Laboratory testing

Site investigation works and factual reporting is being undertaken for a number of suburbs that were affected by liquefaction induced land damage.

The report contains factual data to provide a geotechnical source for council consent applications for the suburb. This report presents all currently available geotechnical and engineering geological investigations that were commissioned by EQC after the 2010 Darfield Earthquake and all readily available data that Environment Canterbury and Waimakariri District Council hold for the suburb.

This is a factual report of field investigations. The field investigations have been undertaken at discrete locations and no inferences about the nature and continuity of ground conditions away from the investigations locations are made. No interpretation of investigation results has been made in this report.

2 Project background

The magnitude (M) 7.1 Darfield Earthquake occurred on 4 September 2010. The epicentre was close to the town of Darfield, approximately 40 km west of Christchurch. The earthquake caused extensive ground liquefaction, in localised areas of Canterbury. The liquefaction resulted in major ground settlement, lateral spreading and, to a lesser extent, foundation support failure, with consequential building damage.

T&T carried out a broad geotechnical land damage assessment and mapping of the main urban areas in the Canterbury region that have been significantly affected by strong ground motion arising from the earthquake. The results of that assessment are presented in the T&T Stage 1 report (Ref 1) dated October 2010 and released to the general public by EQC. The Stage 1 report presented the land damage categorisation, mapping methodology, information and results generated to 1 October 2010. Land remediation concepts and generalised land remediation options were also presented.

The T&T Stage 2 report (Ref 2) dated November 2010 and released to the general public by EQC is based on a detailed suburb-by-suburb engineering assessment into the nature and extent of land damage. It also identifies land repair strategies for each suburb and areas most affected by land damage. The report presents 22,500 mapped properties as at 5 November 2010 in Canterbury and separates them into three recovery zones; A, B and C. These recovery zones relate to the extent of land repair required and allow for a coordinated recovery plan.

2



3 Site description

3.1 General

The subject area of Avonside is located approximately 2.5 km north east of Christchurch CBD and within the Christchurch City Council jurisdiction. The subject area of Avonside is on the south bank of the Avon River with the river defining its northern, western, and eastern boundary The extent of the subject area considered in this report is shown on Drawing LOC-AVS-01, Appendix A.

The area is low lying and topographically is typically flat.

3.2 Regional geology

The Geology of the Christchurch Urban Area (Ref 3) shows that the subject area of Avonside is underlain by alluvial sand and silt overbank deposits around the banks of the Avon River. The centre of the subject area is shown to be underlain by sand of fixed and semi-fixed dunes and beach deposits of Holocene age.

4 Geotechnical investigations

4.1 General

The geotechnical investigations commissioned by EQC from September 2010 were determined and located under direction from T&T. The locations were selected taking into account access for the site investigation plant, the presence of services and any traffic management requirements. The current investigations comprise:

(a) 31 Cone penetration tests (CPTs)

(b) 7 Machine drilled boreholes

(c) 1575 m of MASW geophysical testing

(d) Laboratory testing

The location of the site investigations is shown on Drawing GIP-AVS-01 (Appendix A) and each of the above investigation techniques is discussed below.

4.2 Cone penetration testing (CPT)

Five companies were commissioned to provide CPT probing services on this project and information on the CPT rig capability is summarised briefly below. The output of each CPT rig varies and therefore the testing data has been produced on a standard T&T template. The company which carried out each CPT test is identified on the CPT log. The companies that carried out the testing were:

a) Opus International Consultants Ltd (Opus) - 18T truck-mounted rig b) Perry Drilling Ltd (Perry) - 20T rubber tracked truck-mounted rig c) McMillan Drilling Services (McMillan) - 14T truck-mounted rig d) Geotech Drilling (Geotech) - 16T truck-mounted rig e) Ground Investigations Ltd (GI) - self-augering Pagani CPT rig. The rig augers reaction

anchors into place in the ground in order to drive a standard CPTu cone with up to 20T of force.

Selected CPT probes had down-hole seismic shear wave velocity testing carried out. These are identified on each CPT log and summarised in Table 4-1 below.

3



Each CPT probe location was pre-dug by hand to between 800 mm and 1200 mm to mitigate the risk of unforeseen underground services being present at the selected investigation locations.

The results of the CPT probing are presented in Appendix B.

The CPT testing undertaken is summarised in Table 4-1.

Table 4-1 Cone penetration testing summary

CPT ID Maximum depth (m) Comments

CPT-AVS-01 6.86 Pilot CPT





CPT-AVS-06 4.12

CPT-AVS-07 22.55

CPT-AVS-08 13.49

CPT-AVS-09 6.31 Seismic CPT

CPT-AVS-10 19.10

CPT-AVS-11 5.49

CPT-AVS-12 23.88

CPT-AVS-13 7.48


CPT-AVS-15 23.82


CPT-AVS-17 23.92

CPT-AVS-18 24.21

CPT-AVS-19 4.60

CPT-AVS-20 29.16



CPT-AVS-23 22.90

CPT-AVS-24 27.90

CPT-AVS-25 27.42

CPT-AVS-26 12.28

CPT-AVS-27 16.82


CPT-AVS-29 28.35

4



CPT-AVS-30 28.12

CPT-AVS-31 25.06

4.3 Machine boreholes

Three companies were commissioned to provide borehole drilling services on this project. Their rig capabilities are briefly discussed below. Each borehole log identifies the company which conducted the drilling.

a) McMillan Drilling Ltd (McMillan) used a direct push drilling rig with Standard Penetration Tests (SPT) at typically 1.2 m centres where appropriate. The direct push yields nearly continuous core recovery and generally extended to a minimum depth of 15 m with core diameter of 50 mm.

b) CW Drilling (CW) used machine drilled rotary coring with Concentrix casing. Samples were recovered using a combination of push tubes and open barrel coring in sediments. Very dense gravels were drilled using an air flush down hole hammer. SPTs were carried out at typically 1.5 m intervals where appropriate.

c) Perry Drilling (Perry) used a John Deere 3720 with HQ coring. Standard Penetration Tests (SPT) were carried out at typically 1.5 m centres. Core diameter recovered was 63.5 mm.

On completion of drilling the boreholes were finished in one of three ways, as listed below:

(a) Backfilling the hole to comply with Environment Canterbury requirements (typically filled with grout or bentonite)

(b) Installation of a piezometer (c) Installation of PVC ducting to enable down-hole shear wave velocity testing.

The recovered core samples were either presented in clear plastic liners or placed into core boxes. The samples were returned to the T&T office in Christchurch for logging, typically within 24 hours of the borehole being completed.

The core recovered from the boreholes was logged by a T&T geotechnician in general accordance with the New Zealand Geotechnical Society Guidelines (Ref 4). Representative samples were selected from the borehole materials for laboratory testing.

The machine boreholes undertaken are summarised in Table 4-2.

Table 4-2 Machine borehole drilling summary

Borehole ID Maximum depth (m) Method Drilling Company

BH-AVS-01 15.00 Concentrix CW Drilling




BH-AVS-05 15.00 Dual Tube McMillian

BH-AVS-06 15.00 Dual Tube McMillian


5



The borehole logs are presented in Appendix C and photographs of the borehole core in Appendix D. A borehole log key sheet is included in the front of Appendix C.

4.4 Geophysical testing

Southern Geophysical Ltd completed a series of geophysics tests at specified locations within the suburb. The testing comprised Multichannel Analysis of Surface Waves (MASW) and was used to provide a shear wave velocity profile with depth. The geophones used were typically spaced at 1.0 m centres, which have produced a vertical profile extending around 13.0 m below ground level. This technique was carried out at approximately 5.0 m centres to provide a two dimensional profile of subsurface shear wave velocities. Copies of the geophysical testing results are presented in Appendix E.

5 Groundwater observations

In Avonside, during the investigations, groundwater depths ranged from 3.0 m to 0.4 m below existing ground level. These identified levels were based on dynamic pore water pressure results in CPT testing and field observations of waterways (river & stream levels).

6 Laboratory testing

Geotechnics Ltd (Tauranga) were commissioned by T&T to undertake various laboratory tests on samples obtained from the investigation boreholes. Samples recovered from boreholes were couriered to Tauranga for soil classification tests. The samples typically comprised disturbed samples.

The tests undertaken include:

(a) Fines content (wet sieve) testing generally in accordance with NZS 4402:1986 Test 2.8.1 (Ref 5)

(b) Particle size distribution testing in accordance with NZS 4402:1986 Test 2.8.1 (Ref 5)

Copies of the results available to date are included in Appendix F.

7 Environment Canterbury information

Additional borehole data, which is held by Environment Canterbury for the subject area, has been included in Appendix G. This data has been reproduced with the permission of Environment Canterbury and forms part of previous investigations undertaken by a variety of geotechnical consultants. Records for boreholes outside of the area covered by this report may be obtained from Environment Canterbury.

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8 References

1. Tonkin & Taylor Ltd (October 2010), prepared for the Earthquake Commission Darfield Earthquake 4 September 2010 Geotechnical Land Damage Assessment & Reinstatement Report STAGE 1 REPORT.

2. Tonkin & Taylor Ltd (November 2010), prepared for the Earthquake Commission Darfield Earthquake 4 September 2010 Geotechnical Land Damage Assessment & Reinstatement Report STAGE 2 REPORT.

3. Brown, L.J.; Weeber, J.H. (1992), Geology of the Christchurch urban area. Institute of Geological & Nuclear Sciences 1:25,000 geological map 1. 1 sheet + 104p. Lower Hutt, New Zealand, Institute of Geological and Nuclear Sciences Limited.

4. NZ Geotechnical Society (December 2005), Field Description for Soil and Rock. Guideline for the Field Classification and Description of Soil and Rock for Engineering Purposes.

5. New Zealand Standards (1986), NZS4402: Methods of testing for civil engineering purposes.

7



REPORT

Earthquake Commission Darfield Earthquake Recovery Geotechnical Factual Report Avonside Appendix A: Investigation Location Plans

Darfield Earthquake Recovery Geotechnical Factual Report Avonside

Appendix A: Investigation Location Plans T&T Ref. REP-AVS-FAC


REPORT



Report prepared by:

TONKIN & TAYLOR LTD

Distribution:



February 2011




AVONSIDE

Environmental and Engineering Consultants

Tonkin & TaylorLevel 6, 151 Kilmore St, Christchurch

Tel. (03) 363-2440 Fax. (03) 363-2441www.tonkin.co.nz

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Environmental and Engineering Consultants

Tonkin & TaylorLevel 6, 151 Kilmore St, Christchurch

Tel. (03) 363-2440 Fax. (03) 363-2441www.tonkin.co.nz

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REPORT

Earthquake Commission Darfield Earthquake Recovery Geotechnical Factual Report Avonside Appendix B: Cone Penetration Testing


Appendix B: Cone Penetration Testing T&T Ref. REP-AVS-FAC


REPORT



Report prepared by:

TONKIN & TAYLOR LTD

Distribution:



February 2011








Summary Sheet – Avonside AVS 14

CPT ID Maximum depth (m)

Location (mE)

Location (mN)

Ground Surface R.L

Comments

CPT-AVS-01 6.86 2483074.19 5742802.94 3.51 Pilot CPT

CPT-AVS-02 5.36 2483222.25 5743460.89 2.58 Pilot CPT

CPT-AVS-03 9.58 2483188.76 5743600.88 2.03 Pilot CPT

CPT-AVS-04 3.52 2483468.90 5743411.64 1.76 Pilot CPT

CPT-AVS-05 8.58 2483243.93 5743203.48 2.95 Pilot CPT

CPT-AVS-06 4.12 2482608.56 5742479.82 2.54

CPT-AVS-07 22.55 2482623.00 5742811.64 2.40

CPT-AVS-08 13.49 2482871.68 5742819.98 2.67

CPT-AVS-09 6.31 2483100.01 5742802.23 3.94 Seismic CPT

CPT-AVS-10 19.10 2483411.49 5742844.61 2.75

CPT-AVS-11 5.49 2482695.06 5742925.60 2.39

CPT-AVS-12 23.88 2483143.51 5742942.76 3.74

CPT-AVS-13 7.48 2483351.79 5742976.05 2.10


CPT-AVS-15 23.82 2482913.03 5743194.15 3.09


CPT-AVS-17 23.92 2483404.97 5743196.28 1.81

CPT-AVS-18 24.21 2482888.42 5743350.61 2.03

CPT-AVS-19 4.60 2483148.56 5743357.67 2.87

CPT-AVS-20 29.16 2483326.95 5743381.77 2.69



CPT-AVS-23 22.90 2483382.51 5743505.67 1.68

CPT-AVS-24 27.90 2483210.54 5743602.16 1.91

CPT-AVS-25 27.42 2483076.50 5743581.76 1.81

CPT-AVS-26 12.28 2483143.19 5743601.07 1.95

CPT-AVS-27 16.82 2483291.52 5743598.21 1.80





CPT-AVS-29 28.35 2483426.85 5743470.10 1.84

CPT-AVS-30 28.12 2483475.74 5743265.50 1.17

CPT-AVS-31 25.06 2483422.36 5743218.89 1.77

Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 1 CPT-AVS-01 Test Date: 30-Sep-2010 Location: Avonside Operator: Geotech Pre-Drill: 0m Assumed GWL: 2.8mBGL Located By: Survey GPS Position: 2483098.6mE 5742789.2mN 4.221mRL Coord. System: NZMG & MSL Other Tests: Comments:

0

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Sleeve Friction (kPa)

Dep

th( m

)

Cone Resistance (MPa)Cone Sleeve

0 1 2 3 4 5 6

0 1 2 3 4 5 6Friction Ratio (%)

0 100 200 300

0 100 200 300Pore Pressure (kPa)

T+T Ref: 51731.001 Printed: 16/12/2010 3:59 p.m. Template: CPT Graph Template v0.41.xls

Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 1 CPT-AVS-02 Test Date: 1-Oct-2010 Location: Avonside Operator: Geotech Pre-Drill: 0m Assumed GWL: 1.8mBGL Located By: Survey GPS Position: 2483222.3mE 5743461mN 2.584mRL Coord. System: NZMG & MSL Other Tests: Comments:

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0 100 200 300



Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 1 CPT-AVS-03 Test Date: 1-Oct-2010 Location: Avonside Operator: Geotech Pre-Drill: 0m Assumed GWL: 1.4mBGL Located By: Survey GPS Position: 2483188.7mE 5743600.9mN 1.999mRL Coord. System: NZMG & MSL Other Tests: Comments:

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Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 1 CPT-AVS-04 Test Date: 30-Sep-2010 Location: Avonside Operator: Geotech Pre-Drill: 0m Assumed GWL: 2mBGL Located By: Survey GPS Position: 2483468.9mE 5743411.6mN 1.782mRL Coord. System: NZMG & MSL Other Tests: Comments:

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Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 1 CPT-AVS-05 Test Date: 1-Oct-2010 Location: Avonside Operator: Geotech Pre-Drill: 0m Assumed GWL: 2.1mBGL Located By: Survey GPS Position: 2483244mE 5743203.4mN 2.943mRL Coord. System: NZMG & MSL Other Tests: Comments:

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Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 1 CPT-AVS-06 Test Date: 15-Dec-2010 Location: Avonside Operator: Opus Pre-Drill: 1.2m Assumed GWL: 2mBGL Located By: Survey GPS Position: 2482608.6mE 5742479.8mN 2.54mRL Coord. System: NZMG & MSL Other Tests: Comments:

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T+T Ref: 51731.001 Printed: 21/12/2010 9:51 a.m. Template: CPT Graph Template v0.41.xls

Project: Darfield 2010 Earthquake - EQC Ground Investigations Page: 1 of 2 CPT-AVS-07 Test Date: 16-Nov-2010 Location: Avonside Operator: Perry Pre-Drill: 0.8m Assumed GWL: 1.9mBGL Located By: Survey GPS Position: 2482623mE 5742811.6mN 2.4mRL Coord. System: NZMG & MSL Other Tests: Comments:

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