839080 E

839100 E

839120 E

839140 E

839160 E

839180 E

839200 E

839220 E

839240 E

830200 N

830220 N

830240 N

830260 N

830280 N

830300 N

830320 N

830340 N

830360 N

surveyed

designed

drawn

traced

checked

name date

REVISION

no. date description initial

examined

contract no.

file no.

job no.

project

drawing title

drawing no. scale

officePLANNING DIVISION

GEOTECHNICAL ENGINEERING OFFICE

Y.L.Lee

8/97

1:350EG503

GCP2/E2/13-2

LAI PING ROADLANDSLIDE

INVESTIGATION

1 Final draft NPK

S. D. G. Campbell and N.P.Koor

S. D. G. Campbell and N.P.Koor

1/98

1/98

2/98

3/98N.P.Koor

N.P.Koor

830380 N

830400 N

839260 E

6/1998

FEATURES OF THE COMPOSITELANDSLIDE AND GROUND

INVESTIGATION LOCATIONS

7/98C.J.N.Fletcher

2 SDGC9/1998 Camera positions added plus minor amendments

CIVIL

ENGINEERING

DEPARTMENT

1

2

Sharp Scarp

Width of open crack

Dip and strike of surface of rupture

Dip and strike of joint

Dip and strike of strata

Slope of surface74°

72°

45°

70°

72°

60°

60°

Surface of rupture containingslickensides with plunge andplunge direction

Joint surface containingslickensides with plunge andplunge direction

Dip and strike of volcanic fabric20°

Vertical joint

Dip and strike of quartz vein80°

839080 E

839100 E

839120 E

839140 E

839160 E

839180 E

839200 E

839220 E

839240 E

830200 N

830220 N

830240 N

830260 N

830280 N

830300 N

830320 N

830340 N

830360 N

NOTES :

2. LEGEND :

1. THE SURVEY IS BASED ON THE HONG KONG (1980) GRID SYSTEM.

Ridge line - sharp

Concave break in slope - sharp

Tension crack

Concrete surface water U-channel

Spring point with persistent flow

Spring point with impersistent flow

Block sample location

Sand replacement test location

BS 1

SR 8

Dip and strike of flow banding

Dip and strike of joint and surface ofrupture20

20

50°

Dip and strike of joint and surface ofrupture containing slickensides withtrend and plunge direction

85

PW0/30

PW30/50

PW50/90

PW90/100

Landslide debris

Reworked landslide debris

Colluvium

Made ground

Zone of intense alteration

Rhyolite dyke

Disrupted vegetated raft oflandslide debris

surveyed

designed

drawn

traced

checked

name date

REVISION

no. date description initial

examined

contract no.

file no.

job no.

project

drawing title

drawing no. scale

officePLANNING DIVISION

GEOTECHNICAL ENGINEERING OFFICE

Y.L.Lee

8/97

1:350EG503

GCP2/E2/13-2

LAI PING ROADLANDSLIDE

INVESTIGATION

Concave break in slope - rounded

1 Final draft NPK

M

K

S. D. G. Campbell and N.P.Koor

S. D. G. Campbell and N.P.Koor

1/98

1/98

2/98

3/98

rh

N.P.Koor

N.P.Koor

830380 N

830400 N

839260 E

Stream (dry)

Stream, arrow shows flow direction

Retaining structure

Boundary of Fill Mound -Post-1997 Failure

Failure scarp - minor - failures1-5

Failure scarp - main - failures 1-5

DH97/6

HE6

56A/BH7

Trial Pit No. 56/TP4Geotechnics and Concrete Engineering(H.K.) Ltd (1995) Slope Stabilisation toKau To Borrow Area, Area 59, Shatin

56A/TP4

BH5

BH303

DH97/03

Hand Excavated Trial Pit HE13Enpack (Hong Kong) Ltd. (1998)Phase II G.I. - Lai Ping Road LandslideInvestigation

Hand Excavated Trial Pit No. HE6Enpack (Hong Kong) Ltd. (1998)Phase I G.I. - Lai Ping Road LandslideInvestigation

HE13

13.0

18.6

15.2

12.5

12.5

10

HET1 Hand Excavated Trial Trench HET1

Isopachs, in 5m intervals of saprolitethickness - 15m isopach shown in bold

P1>15.2

Drillhole No. BH303,Saprolite thickness ( ) in metresLam Construction Co., Ltd. (1979)Kau To Borrow Area Investigation

12.5

Drillhole No. BH5,Saprolite thickness ( ) in metresEnpack (Hong Kong) Ltd. (1992)Kau To Salt Water Service ReservoirGround Investigation

15.2

Drillhole No. 56A/BH7,Saprolite thickness ( ) in metresGeotechnics and Concrete Engineering(H.K.) Ltd (1995) Slope Stabilisation toKau To Borrow Area, Area 59, Shatin

18.6

Drillhole No. DH97/6,Saprolite thickness ( ) in metresEnpack (Hong Kong) Ltd. (1998)Phase I G.I. - Lai Ping Road LandslideInvestigation

13.0

Drillhole No. DH97/03,Saprolite thickness ( ) in metresEnpack (Hong Kong) Ltd. (1998)Phase II G.I. - Lai Ping Road LandslideInvestigation

12.5

>15.2Drillhole No. P1,Saprolite thickness ( ) in metresLam Construction Co., Ltd. (1980) -Tin Salt Water Header Tank Investigation

Limit of colluvium >1m thick

Base topography taken from CED Survey DivisionDrawing Number GCS2627/IA1-2)

Legend :

< 2.0 %

< 4.0 %

N

< 6.0 %

< 8.0 %

< 10 %

Number of poles : 181

86 ° / 098 °

49 ° / 198 °

75 ° / 207 °

28 ° / 001 °3

3

2

2

1

1

44

49° /198°1

Number of poles : 52

< 10.0 %

< 12.5 %

< 15.0 %

Legend :

< 2.5 %

< 5.0 %

N

< 7.5 %

80 ° / 139 °

55 ° / 175 °

43 ° / 216 °

75 ° / 246 °

71 ° / 226 °

194 °

B

C

D

E

A

A

B

C D

E

Main d i rec t i ono f l ands l i demovement

189 °

80° /139°A

Number of poles : 54

< 14.0 %

< 17.5 %

< 21.0 %

Legend :

< 3.5 %

< 7.0 %

N

< 10.5 %

189 ° / 52 °

194 ° / 64 °

337 ° / 67 °

Le f t handf lank

Reverse sca rpson g rabens

189° /52°

1

4

3

2 1

5

7

Legend :

6

4

5

6

7

3

2

1

Dip/Dir. Remark

- Unstable zone where slope oversteepened to 55° locally due to instability at the cut face

1

49°/198°

75°/207°

28°/001°

86°/098°

Ø=20°

N

7Original cut slope

Remark

55°/220°

33°/192°

33°/220°

Possibleoversteepenedslope

Trend and plungeof slickensides

Dip and dip directionof main and minorscarps

Dip and dip directionof major jointconcentrations

Kinematic slope stability plot for plane and wedgefailure associated with the four major joint sets

6/1998

6'

6

Line of geological section

Residual soils - also including old colluvium

Contoured plot of main and minor scarps

Contoured Plot of trend and plunge of slickensides on surfaces of rupture

Contoured plot of joint surfaces

Coarse ash TUFF, rockmass weathering grade

Manganiferous infill to planar discontinuity

Kaolinitic clay infill to planar discontinuity

Major andMinor Scarps

Active scarp 1997

FEATURES OF THE COMPOSITELANDSLIDE AND GROUND

INVESTIGATION LOCATIONS

7/98C.J.N.Fletcher

2 SDGC9/1998 Camera positions added plus minor amendments

All stereonets are equal anglelower hemisphere nets. Data are uncorrected.

Majordiscontinuitysets

CIVIL

ENGINEERING

DEPARTMENT

Ø=30°

Ø=10° 1

2

Ø=10° - Friction Angle

v

100

105

110

115

100

105

110

115

125

130

135

140

145

95

115

120

125

120

140

145

150

155

150

155

150

145

140

135

130

110

105

100

95

90

115

120

125

L A I P I N G R O A D

??

? ? ??

160

165

170

165

160

165

160

170

175

175

155

170

175

135

130

125

120

115

Covered Salt Water Reservoir

Failedpre-1997

Gul

ly er

oded

into

deb

ris

Landslide Scar 5

LandslideScar 3B

LandslideScar 3

LandslideScar 1

Landslide Scar 4

complex tensioncrack system

DH97/6

DH97/7

DH97/9

DH97/10

DH97/11

DH97/13

DH97/12

DH97/14

DH97/15

DH97/17A

TT1

TT2

HE1

HE2

HE2A

HE3

HE5

HE6

HE8

HE9

56A/TP1

56A/TP2

56A/TP3

56A/TP4

56A/TP5

56A/TP6

BH1

BH2

BH3

BH4

BH5

BH6

BH7

BH8

BH9

BH302

BH303

BH304

BH305

BH306

BH307

DH97/02

DH97/03

DH97/08

DH97/18

DH97/20

DH97/21A

DH97/22

TT2A

HE13

HET1

Area ofDense vegetation

Landslide Scar 4A

Dense vegetation

6.3

0.6

7.4

7.9

7.4

7.1

5.9

15.2

15.6

>20.7

36.3

32.6

12.5

11.5

13.0

12.5

13.217.9

21.9

22.4

20.9

12.4

17.3

23.5

18.1

16.8

21.5

15.3

20.5

18.6

7.914.0

14.0

>15

14.7

P1

P2 P3

P5

>15.2

9.5 >16

14

Reworked debris extendsfurther down slope

Eroded Debris

See Figure 1 forContinuation ofSection Line 6 - 6'

in situvegetation

in situvegetation

in situvegetation

in situvegetation

Fill mound, comprising debris from April 1997,

erosion of landslide 3

Original cutslope face

P1

P2 P3

P5

>15.2

9.5 >16

14

62°

48°

41-56°

62°

33°

54°

46°

20°

65°SL

68°49-40°

70-85°

81-90°

75-83°

70°

71°

58°

72°

72°

76°

76°

71°

79°

74°

53°

75°80°

70°

68°

65°65°

88°59°

87°

64°

65°

70°

67°

Grave

74°

81°

86°82°

71°

84°84°

64°

30° 66°

35°

80°60°58°

65°77°

80°80°

64°67°

72°

82°

30° 79°79°

51°

62°

88°

54°

74°

56°64°

74°

80°

80°62°

85°

62°47°

45°42°

15°

89°33°

85°

70°

82°

75°

87°

63°55°

68°70°

85°

82°76°

76°

74°

79°

75°

72°

74°

15°

82° 82°

27°82° 29°80°

80°

18°65°

50°88°

15-18°

0-24°

40°

25°

15-20°

47-60°

25°

17°

AREA OF DENSE VEG

ETATION

52°

68°

70°67°

68°80°

85°

80°80°

60°53°

40°

63°

82°52°

81°

32°

85°

68°80°

66°50°

35°

67°

88°

60°

54°

78°

52° 38°61°85°

87°

85°82°

82°

82° 87°34°

78°

80°77°

88°88°89°

43°75°

85°65°

83°

83°

53°

30°35°

86°

52° 82°

57°

69°

36°

83°56°

33°

15-35°

86°

76°30°

55°

84°

64°

56A/BH1

56A/BH2

56A/BH3

56A/BH4

56A/BH5

56A/BH6

56A/BH7

56A/BH8

0.6

0.4

18.6

23.9

15.3

5.53

9.3

20.2

4063

BS 2BS 1

SR 8 SR 9

SR 10

BS 3

SR 7

SR 6

BS 4

BS 5SR 5

BS 6BS 7

SR 3

SR 4

BS 9

BS 864

85

4855 50

KMKM 54

K50

M75

53MK

56

48 45

3554

M66

Q75

K65

40-44K

51 K

6080

85

4552

48K

80

80

83

50

50

BS 12

BS 11 BS 10

6734

3454

K

76

M83

51

61

81 38 M

81

MK

MK(10mm)26

MK52

50

K72

M

58

SR 2

40

55

3275

75

5556

4545

4532

48

48

80

45

55

80

20

rh

rh

rh

rh

rh

rh

rh

rh

rh

rh

rh

rh

K

rh

Landslide Scar 3A

LandslideScar 2

The Site

Site Location Plan

Oldlandslide scar