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FOREWORDThis Report aims to provide an adequate geotechnicai basis for the planning and land use management ofthe Central New Territories, mainly by way of information presented on a series of maps at a scale of1:20 000. It is the second of twelve reports to be published as a result of the Territory-wide Geotechnicai AreaStudies Programme (GASP) carried out by the Geotechnicai Control Office between 1979 and 1985.GASP is based largely on terrain classification techniques using aerial photographs, together with fieldreconnaissance and the evaluation of a large number of existing site investigation records. It employs aunique system of terrain evaluation developed especially for Hong Kong conditions for the analysis andinterpretation of the available data.The GASP Reports were originally conceived as providing information almost solely for territorial land useplanning, for which purpose the mapping scale of 1:20000 is considered to be suitable. However, theinformation they contain also provides a good basis for engineering feasibility studies of large sites. Theoverall geotechnicai assessment of a study area is presented on a series of seven user-oriented maps. Four ofthese are supplied with this published Report—the Engineering Geology Map (EGM), Geotechnicai LandUse Map (GLUM), Physical Constraints Map (PCM), and Generalised Limitations and EngineeringAppraisal Map (GLEAM). The GLUM classifies the terrain into four classes according to the level ofgeotechnicai limitations, the PCM presents the major physical constraints that are likely to influencedevelopment, and the GLEAM delineates broad areas with potential for development from the geotechnicaiand planning points of view. In addition to the four maps accompanying this Report, the TerrainClassification Map, Landform Map and Erosion Map can be consulted in the Geotechnicai Information Unitof the Geotechnical Control Office.Users of GASP Reports should make reference to the new 1:20 000 scale Hong Kong Geological SurveyMaps and Memoirs which are being prepared by the Geotechnical Control Office. These provide more up todate geological information than is available in this Report. The Geological Map which covers the Sha Tin area,together with the accompanying Memoir, has recently been published (Geotechnical Control Office, 1986;Addison, 1986).This Report was originally produced in May 1985, for use within the Hong Kong Government on the basisof information assembled during the period March 1980 to October 1984. This fact should be borne in mindby users, who should also note that the contents of the Report have for the most part not been updated.Further, although every effort has been made to ensure the accuracy of the information contained in theReport, this cannot be guaranteed. The Geotechnical Control Office cannot therefore accept any liability forerrors in the data or for misinterpretations made during the study.It must be emphasised that this document was prepared for general planning and resource evaluationpurposes. As a general rule, 1:20000 scale maps, particularly the GLUM, should not be used to evaluateparcels of land smaller than 3 hectares in size, and should never be interpreted, reproduced or enlarged toa scale greater than 1:20000. Failure to heed this warning could result in serious misinterpretation of theinformation they contain.The GASP study was undertaken by a team of specialist Geotechnical Engineers in the Planning & TerrainEvaluation Section of the Planning Division of the GCO, which included Messrs D. C. Cox, A. Hansen,P. D. Houghton, R. J. Purser and K. A. Styles. The Planning & Terrain Evaluation Section is led byMr K. A. Styles, and the Planning Division is under the direction of Dr A. D. Burnett.The Geotechnical Control Office acknowledges the co-operation and assistance given by the Commissionerof the Soil Conservation Service of New South Wales, Australia, who made available Mr P. D.Houghton, a specialist Aerial Photograph Interpreter, to participate in the study. Acknowledgements are alsodue to the Lands Department of the Hong Kong Government, who provided most of the aerial photographsused in the study, a few of which are reproduced in this ReportE. W. BrandPrincipal Government Geotechnical EngineerSeptember 1987
CONTENTSPageFOREWORD 31. INTRODUCTION1.1 The Central New Territories Geotechntcal Area Study 101.2 The Geotechnical Area Studies Programme 101.3 Aims of the Geotechnical Area Studies Programme 101.4 Organisation of the Report 111.5 Maps Produced within the Regional Study 111.5.1 General 111.5.2 Terrain Classification Map (TCM) 111.5.3 Landform Map (LM) 111.5.4 Erosion Map (EM) 121.5.5 Geotechnical Land Use Map (GLUM) 121.5.6 Physical Constraints Map (PCM) 121.5.7 Engineering Geology Map (EGM) 121.5.8 Generalised Limitations and Engineering Appraisal Map (GLEAM) 121.5.9 Computer-generated Maps 131.6 Suitability of the Maps for Technical and Non-Technical Use 131.7 GASP District Studies Relevant to the Study Area 131.8 Access to GASP Data 142. DESCRIPTION OF THE CENTRAL NEW TERRITORIES STUDY AREA 152.1 Geographical Location 152.2 Topography 152.3 Geology 152.3.1 General 152.3.2 Metamorphic Units—Tolo Harbour Formation 162.3.3 Volcanic Units—Repulse Bay Formation 162.3.4 Intrusive Igneous Units 172.3.5 Superficial Units 172.4 Geomorphology 182.4.1 General 182.4.2 Granitic Terrain 182.4.3 Volcanic Terrain 192.4.4 Colluvial Terrain 192.4.5 Alluvial Terrain 1 g2.5 Surface Hydrology 202.6 Vegetation 202.7 Erosion and Instability 212.7.1 General 212.7.2 Erosion 222.7.3 Instability 2241 0
Page 2 and 3: THE UNIVERSITY OF HONG KONGLIBRARY
Page 5: Map of the Territory of Hong Kong S
Page 9 and 10: PageA.8 Engineering Geology Map 111
Page 11 and 12: List of FiguresFigure TitlePage1 Lo
Page 13 and 14: 1.1.1 The Centra! New Territories G
Page 15 and 16: 1.5.4 Erosion Map (EM)This map is t
Page 17 and 18: Table 1.3 GLUM Classes and Landslip
Page 19 and 20: The geological boundaries for the b
Page 21 and 22: (a) Volcanic coiluvium (Cv)—This
Page 23 and 24: The most common occurrence of this
Page 25 and 26: Areas subject to erosion are classi
Page 27 and 28: SquattersSquatters appear to be loc
Page 29 and 30: 3. ASSESSMENT OF3.1 Description and
Page 31 and 32: material density but undisturbed sa
Page 33 and 34: Table 3.1Description and Evaluation
Page 35 and 36: As with the volcanic rocks, the fre
Page 37 and 38: The steep terrain and thin weathere
Page 40 and 41: Reference should be made to the Geo
Page 42 and 43: Area 6Area 7Area 8Area 9Tai Mo Shan
Page 44 and 45: The area is entirely underlain by v
Page 46 and 47: Approximately 5% of the terrain has
Page 48 and 49: Most of the ridgecrest terrain fall
Page 50 and 51: 5.The findings reached during the C
Page 52 and 53: 6.Addison, R. (1986). Geology of Sh
Page 54: So, C. L (1971). Mass movements ass
Page 57 and 58:
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Page 59 and 60:
CLASS IV (26.0%) /UNCLASSIFIED (2.0
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F F A R Rx, v v R R flv A >- ( R R
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+ + ® m+ *-*=[_! 5-Bailie]*;*- + *
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I1 Fig. 1Location map ofthe Central
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W TP flj? W-fi I OIM INUIIixTYa-n'
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Scale1:20 000Example of the Geotech
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Scale1.20 000Example of the Physica
Page 78 and 79:
Scale1:20 000Example of the Enginee
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Scale1:20 000Example of the General
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Example of the Landform Map (LM)Sca
Page 84:
Scale1:20 000Example of the Erosion
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Plate 2.Oblique Aerial Photograph L
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Plate 4. Oblique Aerial Photograph
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Plate 6.Oblique Aerial Photograph o
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Plate 8.Oblique Aerial Photograph o
Page 96 and 97:
Plate 10. Low Level Oblique Aerial
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Plate 12. Ridgecrest Erosion on the
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1 S';: ; f -;,Plate 14.Low Volcanic
Page 102 and 103:
Plate 16.Upper Sideslope and Ridgec
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BBBBI BHHH........ ... :,.;, • Il
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AOF EVALUATION ASSOCIATED TECHNIQUE
Page 108 and 109:
GeneralisedLimitations andEngineeri
Page 110 and 111:
In this study, all the footsSope an
Page 112 and 113:
A.7 Geotechrsical Land Use MapThe G
Page 114 and 115:
(b) Records of a limited amount of
Page 116 and 117:
A.9 Generalised Limitations and Eng
Page 118 and 119:
Table A4Criteria for Initial Assess
Page 120 and 121:
The information presented in the GL
Page 122 and 123:
APPENDIX BTableDATA TABLES FOR THE
Page 124 and 125:
Table B4 Aspect and Slope GradientA
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Table B8Geology and GLUM ClassGeolo
Page 128 and 129:
Table B10Slope Gradient, Aspect Geo
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Table B12Existing Land Use (From ae
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cINFORMATIONPageC.1 Description of
Page 134 and 135:
Jointing within this rock type is u
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6040Marine deposit - sands, silts a
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The rock is pale grey or pink when
Page 141 and 142:
Within Tide Cove itself, this basal
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of Reports4 - 6per §riil black hel
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RAINFALL(mm)ro14s*en c33Q)CD3O 3339
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Table C2Selection of Aerial Photogr
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DOF AND CHARACTERISTICS ONIN HONG K
Page 151 and 152:
The more randomly oriented, smoothe
Page 153 and 154:
ROCKMASSCHARACTERISTICSJOINTSFAULTS
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D.2.5FaultsA fault is a fracture in
Page 157 and 158:
(e) Basements—these require tanki
Page 159 and 160:
(iv) S/te InvestigationIn heterogen
Page 161 and 162:
D.3.11Site InvestigationA 'desk stu
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Irregularities in slope profile can
Page 165 and 166:
CHUNAMCement-lime stabilised soil u
Page 167 and 168:
INCISED DRAINAGE CHANNELTerrain com
Page 169 and 170:
SHEETING JOINTDiscontinuity produce
Page 171 and 172:
This book is due for return or rene
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