Christchurch Factual Report
Total Page:16
File Type:pdf, Size:1020Kb
REPORT Earthquake Commission Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City REPORT Earthquake Commission Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City Report prepared for: EARTHQUAKE COMMISSION Report prepared by: Tonkin & Taylor LTD Distribution: EARTHQUAKE COMMISSION 1 copy Tonkin & Taylor LTD (FILE) 1 copy December 2011 T&T Ref: REP-CCM-FAC Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City T&T Ref. REP-CCM-FAC Earthquake Commission December 2011 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) 3 4.3 Machine boreholes 5 5 Laboratory testing 6 6 Environment Canterbury information 6 7 References 6 Appendix A: Investigation Location Plans and Geotechnical Investigations A0 - Key Map A1 - Papanui, Merivale and Fendalton areas A2 - St Albans area A3 - Richmond and Avonside areas A4 - Burwood and Avondale areas A5 - Aranui, New Brighton and North New Brighton areas A6 - Hoon Hay, Spreydon, Somerfield, Cashmere and Beckenham areas A7 - Waltham, Opawa, St Martins and Sydenham areas A8 - Woolston area A9 - Bromley area A10 - Southshore area A11 - Styx area A12 - Cone Calibration Certificates Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City T&T Ref. REP-CCM-FAC Earthquake Commission December 2011 1 1 Introduction The Earthquake Commission (EQC) engaged Tonkin & Taylor (T&T) to undertake site investigations around selected suburbs of Canterbury following the Christchurch 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, and, 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. This report only contains factual geotechnical information and is intended to provide a source of geotechnical data to support council consent applications for the suburb. This report presents all currently available geotechnical and engineering geological investigations that were commissioned by EQC during 2010/2011 and all readily available data that Environment Canterbury (ECan) and Christchurch City Council (CCC) 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 Christchurch earthquake sequence began with a magnitude (M) 7.1 earthquake (the Darfield Earthquake) which occurred on 4 September 2010. The epicentre of this earthquake was located close to the town of Darfield, approximately 40 km west of Christchurch. A (M) 6.3 earthquake (the Christchurch Earthquake) occurred on 22 February 2011. The epicentre of this earthquake was located close to Lyttelton, approximately 11 km south-east of Christchurch City. A further (M) 6.3 earthquake occurred on 13 June 2011. The epicentre of this earthquake was located approximately 10km east of Christchurch City. These earthquakes caused extensive ground liquefaction in localised areas of Canterbury and Christchurch City. The liquefaction resulted in major ground settlement, lateral spreading and, to a lesser extent, foundation support failure with consequential building damage. T&T have 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 these earthquakes. 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. Further land damage mapping and assessments were carried out by T&T after the 22 February 2011 and 13 June 2011 Christchurch aftershock events. The results of these assessments were summarised prior to issue to the NZ Government to assist them in their decision making Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City T&T Ref. REP-CCM-FAC Earthquake Commission December 2011 2 process. The Canterbury Land Information Map for residential properties was publicly announced by the NZ Government and Canterbury Earthquake Recovery Authority (Cera) on 23 June 2011. Specific areas within the suburbs named in this report have been subjected to EQC commissioned geotechnical investigations following the 22 February 2011 Earthquake. (Ref. 6) This report details investigations that have been carried out on behalf of EQC at discreet locations beyond the investigation boundaries referred to above. Investigations at a number of locations described within this report have been preparatory to ongoing geotechnical and ground water monitoring. 3 Site description 3.1 General The suburbs covered by this additional geotechnical factual report include: Papanui, Merivale, St Albans, Richmond, Avonside, Avondale, New Brighton, North New Brighton, Hoon Hay, Spreydon, Somerfield, Beckenham, Cashmere, Waltham, Opawa, Sydenham, St Martins, Woolston, Bromley, Styx, Aranui, Burwood and Southshore. The major waterways within or adjoining these suburbs include the Avon and Heathcote Rivers, Avon and Heathcote Estuary, the Pacific Ocean and many smaller streams. With the exception of the hillside areas of the suburb of Cashmere the subject areas are typically low lying and topographically are typically flat. 3.2 Regional geology The publication “Geology of the Christchurch Urban Area” (Ref 3) shows that those areas of Christchurch City that are covered by this additional geotechnical testing are typically underlain by one of four geological formations. 1) Sand of fixed and semi-fixed dunes of marine origin, 2) Sand, silt and peat of drained lagoons and estuaries, 3) Peat swamps, now drained, and, 4) Alluvial sand and silt overbank deposits. All geological deposits are of Holocene age. 4 Geotechnical investigations 4.1 General The geotechnical investigations which were commissioned by EQC following the Canterbury Earthquakes (2010/2011) were scoped and located under the direction of T&T. The locations were selected taking into account access for the site investigation plant, the presence of services and any traffic management requirements. Investigations which were completed subsequent to the Christchurch Earthquake (22 February 2011) comprise: a) 53 Cone penetration tests (CPTs), b) 9 Machine drilled boreholes, and, c) Laboratory testing. The location of the site investigations are shown on Drawings GIP-CCM-A1 to GIP-CCM -A11 (Appendix A1 - A11) and the above investigation techniques are discussed below. Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City T&T Ref. REP-CCM-FAC Earthquake Commission December 2011 3 4.2 Cone penetration testing (CPT) Four 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, and, d) Geotech Drilling Ltd (Geotech) - 16T truck-mounted rig. The Cone Calibration Certificates for each of the above CPT rigs are presented in Appendix A12. Selected CPT probes had down-hole seismic shear wave velocity testing carried out. These are identified on each CPT log and are summarised in Table 4-1 below. Each CPT probe location was pre-dug by hand to a depth of 1.2m to mitigate the risk of a clash with and damage to underground services at the investigation locations. The CPT test location details are summarised below in Table 4-1. Table 4-1 Cone penetration testing summary Suburb CPT ID Depth Location Location Ground Ground Comments (m) (mE) (mN) Surface Water RL Depth (m) APPENDIX A1 Papanui CPT-PAI-19 10.38 2478201.49 5745949.01 13.46 1.30 Merivale CPT-MRV-26 4.28 2478463.60 5743969.96 10.36 1.29 Piezometer installed APPENDIX A2 St Albans CPT-STA-42 6.28 2479733.29 5745155.09 7.03 0.20 St Albans CPT-STA-56 16.66 2481586.02 5744664.18 4.44 0.72 Piezometer installed St Albans CPT-STA-57 13.68 2481801.44 5744879.21 5.35 2.00 St Albans CPT-STA-58 12.56 2481862.00 5744643.09 5.04 0.91 Piezometer installed APPENDIX A3 Richmond CPT-RCH-40 4.50 2482502.10 5742760.07 3.50 Richmond CPT-RCH-42 8.50 2482562.14 5742539.64 2.11 1.50 Richmond CPT-RCH-43 26.12 2482476.47 5742429.41 2.19 0.86 Piezometer installed Richmond CPT-RCH-44 23.56 2482350.58 5742427.24 2.55 2.00 Richmond CPT-RCH-45 7.16 2482429.93 5742518.51 3.11 2.00 Richmond CPT-RCH-46 9.06 2482431.33 5742730.97 4.06 2.33 Piezometer installed Richmond CPT-RCH-72 12.84 2482458.21 5743888.63 2.92 Avonside CPT-AVS-59 25.61 2484440.05 5742676.44 3.20 2.20 APPENDIX A4 Avondale CPT-AVD-62 36.23 2485921.89 5745064.83 1.45 2.60 APPENDIX A5 New Brighton CPT-NBT-50 44.86 2488267.56 5744523.13 3.90 2.70 NN Brighton CPT-NNB-09 41.36 2487244.00 5745668.27 3.38 1.60 Christchurch Earthquake Recovery Geotechnical Factual Report Christchurch City T&T Ref.