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- 6 -In Phase 2 the Group 1 and 2 techniques were further tested at four new sites againconsisting of, two pre-war masonry walls, one cut slope and one fill slope. The Phase 2 sites hadno existing ground investigation data so as to allow the Working Group to assess if thegeophysical methods alone can be reliable and accurate without any pre-conceptions of the siteconditions. Preliminary interpretations were made by each of the contractors based solely on thegeophysical results. Subsequent conventional ground investigations by GEO were then carriedout at the sites and the results were given to each of the contractors for re-interpretation of theirgeophysical results.The Phase 2 trials concluded that the overall quality of the raw data and interpretationsvaried significantly with the expertise of the individual geophysics teams. Certain contractorswere able to demonstrate that a combined geophysical investigation utilising GPR and RI canlocate the back of masonry walls if they are less than 3m thick and define zones of elevatedmoisture content and voids with reasonable accuracy. Only limited success was achieved indetermining the location of corestones and the thickness of loose fill at the two slope sites.In the light of the conclusions from the field trials, it is recommended that due to theinconsistent raw data and interpretations it would not be advisable at present to let a termcontract specifically for non-invasive geophysical techniques for site characterisation in HongKong, or to require the use of such techniques in LPM studies. Also, further trials of the four orother techniques are not warranted. However, since some of the results were encouraging it isrecommended that further research work on developing GPR and RI for masonry wallinvestigations is carried out through a local University with support from GEO. The researchshould focus on ways to enhance the resolution of the two techniques and also to develop a siteand data processing methodology which would ensure more consistent results from contractors.
- 7 -CONTENTSTitle Page 1PREFACE 3FOREWORD 4ABSTRACT 5CONTENTS 71. INTRODUCTION 102. APPLICATION OF GEOPHYSICS TO SLOPES AND WALLS 112.1 Introduction 112.2 Retaining Structures in Hong Kong 122.3 Natural and Man-made Slopes 132.4 Physical Anomalies Behind Slopes or Walls 13Page3. PHASE 1 FIELD TRIALS 143.1 Introduction 143.2 Phase 1 Field Trial Sites 143.2.1 Trial Site A - Kennedy Town Police Quarters. Feature No. 1411SW-A/C2563.2.2 Trial Site B - Eliot Hall, Hong Kong University. Feature No. 1411SW-AVR7033.2.3 Trial Site C - Sir Ellis Kadoorie School. Feature No. 11SE-A/R39 153.2.4 Trial Site D - Cape Collinson Crematorium. Feature No. 1511SE-D/F193.3 Phase 1 Results 163.3.1 Introduction 163.3.2 Assessment of Results 163.3.3 Shallow Seismic Reflection (SSR) 163.3.4 Spectral Analysis of Surface Waves (SASW) 173.3.5 Resistivity Imaging (RI) 17No.
Page 1: SITE CHARACTERISATIONSTUDY - PHASES
Page 4 and 5: - 2 -© The Government of the Hong
Page 6 and 7: - 4 -FOREWORDThis report presents t
Page 10 and 11: - 8 -3.3.6 Self Potential (SP) 173.
Page 12 and 13: - 10 -1. INTRODUCTIONThe collapse o
Page 14 and 15: - 12 -(v) Zones of enhanced moistur
Page 16 and 17: - 14 -contrasts in electrical, dens
Page 18 and 19: - 16 -A total of 4 drillholes and 1
Page 20 and 21: - 18 -The time-domain electromagnet
Page 22 and 23: - 20 -the GI data, final interpreta
Page 24 and 25: - 22 -4.2.5 Trial Site H - Fill Slo
Page 26 and 27: - 24 -4.4 Ground Investigation4,4.1
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- 69 -APPENDIX ASITE CHARACTERISATI
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- 71 -A.I OBJECTIVETo assess the ca
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- 75 -A.8 PRELIMINARY THOUGHTS ON F
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- 77 -APPENDIX BGEOPHYSICS LITERATU
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- 79 -B.2.5.2 Case Histories 89B.2.
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- 81 -Acoustic P-wave velocity meas
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- 83 -a cut slope were successfully
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- 85 -Analysis of Surface Waves (SA
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- 87 -B.2.4.2 Frequency-Domain Elec
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- 89 -The depth of penetration of a
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- 91 -(vi) Ground Penetrating Radar
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- 93 -Hall, D.H. and Hajnal, Z. (19
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- 95 -Pullan, S.E. & Hunter, J.A. (
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- 97 -Butler, D. & Pedersen, E.P. (
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- 99 -Guenther, M. & Kathage, A.F.
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- 101 -Maynard, K.C. & Field, O.K.
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- 103 -Stokoe, K.H., Nazarian, S.,
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- 109 -Table B2 - A Summary of GPR
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- Ill -Figure Bl - Shallow Seismic
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- 117 -APPENDIX CPROFILES OF CONTRA
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- 119 -C.I PHASE 1 FIELD TRTATSBach
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- 121 -The Institute of Geophysical
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- 123 -LIST OF TABLESTableNo.PageNo
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- 125 -1. Main Contractor :Bachy So
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- 127 -Table C3 - Contractor Profil
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- 129 -1. Main Contractor :Guangdon
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- 131 -Table C7- Contractor Profile
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- 133 -1. Main Contractor:Meinhardt
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- 135 -Table Cl 1 - Contractor Prof
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- 13'1. Main Contractor:Golder Asso
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- 139 -1. Main Contractor:Bachy Sol
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- 141 -Table C17 - Contractor Profi
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- 143 -1. Main Contractor:Guangdong
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- 145 -Table C21 - Contractor Profi
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- 147 -APPENDIX DASSESSMENT OF THE
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- 149 -D.7 THERMAL IMAGING 161D.7.1
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- 151 -exception of TB04. Generally
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- 153 -(c) GSC present pseudo-dispe
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- 155 -interpretations of subsurfac
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- 157 -None of the contractors carr
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- 159 -D.5.2.2 Assessment of the MT
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- 161 -was generally used by all co
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- 163 -LIST OF TABLESTableNo.PageNo
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- 165 -LISTOFPT.ATF.SPlateNo.PageNo
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- 192 -CONTENTSPageNo.CONTENTS 192E
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- 194 -signal to improve the signal
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- 196 -well with the GPR results an
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- 198 -TXST OF FIGURESFigureNo.Page
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GEOTECHNICAL ENGINEERING OFFICE PUB
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Report on the Shum Wan Road Landsli
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Report on the Rainstorm of August 1
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Conventional and CRS Rowe Cell Cons
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Report on the Ching Cheung Road Lan
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Geology of the Western New Territor
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Shan Pui: Superficial Geology (1:5
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GE ° PUbHCati ° nS (eXCept Sheet
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