Table 2. Summary of major landslides in... | Emerald Publishing

Table 2.

Summary of major landslides in Singapore

Landslide	Date	Height	Angle	Comments	Ground conditions	References
Tanjong Gul	Pre 1972	25 m	30°	A benched cut slope. The slide took place in the upper part of the slope and affected about 60 m of the slope length. A vertical backscarp of about 2 m was formed and bulging took place at the toe	Volcanic agglomerate, and shale and residual soils. The rocks were dipping steeply in the same direction as the cut	1
Hillview Estate	1982, 1983, 1984	22 m	13·5°	The first major mass movement started in December 1982 due to fracture of a water pipe, possibly caused by earlier minor movements. Further major movements occurred in March 1983 and March 1984 during heavy rainfall. The landslide involved about 50 000 m³ of material	Residual soils derived from Gombak Norite and colluvium with some recent deposits (Kallang formation) being found at the toe. Failure probably occurred very close to the contact between the residual soil and the underlying weathered norite	1
Depot Road	1978, 1984	40 m	29°	A slope on the northern ridge of Mount Faber. A shallow slip occurred mid-slope in December 1978. The slope was originally benched. A major slide (in the form of a flow) occurred in March 1984 after a period of heavy rainfall	The crest of the slope was fill material. The failure occurred in the bench and resulted in disaggregation of the fill material which then developed into a debris flow¹⁴	1
Fort Canning	1984	40 m	34°	Occurred in Fort Canning Park during heavy rain in March 1984. The failure surface was shallow, about 3 m below the ground surface, but about 1500 m² of the slope started to move. Ground anchors were used to stabilise the slope	Residual soils (Grade VI) formed from the sedimentary Jurong formation	1
Gillman Heights	1985	17 m	34°	A cut slope for the Ayer Rajah Expressway at Gillman Heights showed signs of instability in December 1985. The slope was stabilised using soil nails	Medium dense to dense residual soils (Grade IV and V) derived from the sedimentary rocks of the Jurong formation	1
Admiralty Road	1987			A road cutting. The slope had been recently cut and graded during road widening. The initial failure occurred during a nine day wet period with a total rainfall of 413 mm. The slope failed in five places, two of which involved the whole length of the slope. The slope was regraded but failed repeatedly, each time after a period of heavy rainfall	Fill material of weathered granite overlying deeply weathered in-situ granite	6
Lorong Terigu		24 m	27°	This is part of the cut slopes formed during the construction of the Bukit Timah Diversion Canal. Since construction in the early 1970s a number of slips have occurred along the canal length with Lorong Terigu being the largest. The slip surface was found to be 5 to 6 m below ground surface at its deepest point	Loose to medium dense clayey silt near the surface, becoming very dense below 25 m. Standard Penetration Test (SPT) values varied from less than 10 near the surface to over 50 below 25 m. A weaker zone was observed at around 5 m depth	9
Central business district		17·8 m	53°	A number of slope failures occurred during the construction of a substantial excavation site in the central business district in Singapore. This was the highest slope to fail	Weathered sandstones and shales of the Jurong formation (Rimau facies). Degree of weathering changed from highly to slightly weathered within the top 10 m. The strata dipped steeply back into the slopes. The shale had softened during heavy rainfall	10
Bukit Batok/ Bukit Gombak	1989	40 m	27°	A cut slope at the Bukit Batok sports complex that failed after heavy rain. A backscar of 4 to 6 m was formed by the slide and about 100 m of slope was affected. The slide was 56 m from toe to crest and the maximum depth to the failure surface was 8·5 m. There was continuous rainfall for three days prior to the failure (151 mm in total), but the slope failed about 24 h after the rain stopped. There had also been an exceptionally heavy day of rain (112 mm) 19 days earlier. Water was seen to be flowing out of the slope after failure. Further shallow slides occurred in December 1991 and drainage works were implemented to stabilise the slope¹⁵	The ground conditions comprised highly weathered rock of the Gombak Norite formation. The residual soil of highly decomposed granite consisted of clayey silt with boulders	11

Landslide	Date	Height	Angle	Comments	Ground conditions	References
Tanjong Gul	Pre 1972	25 m	30°	A benched cut slope. The slide took place in the upper part of the slope and affected about 60 m of the slope length. A vertical backscarp of about 2 m was formed and bulging took place at the toe	Volcanic agglomerate, and shale and residual soils. The rocks were dipping steeply in the same direction as the cut	1
Hillview Estate	1982, 1983, 1984	22 m	13·5°	The first major mass movement started in December 1982 due to fracture of a water pipe, possibly caused by earlier minor movements. Further major movements occurred in March 1983 and March 1984 during heavy rainfall. The landslide involved about 50 000 m³ of material	Residual soils derived from Gombak Norite and colluvium with some recent deposits (Kallang formation) being found at the toe. Failure probably occurred very close to the contact between the residual soil and the underlying weathered norite	1
Depot Road	1978, 1984	40 m	29°	A slope on the northern ridge of Mount Faber. A shallow slip occurred mid-slope in December 1978. The slope was originally benched. A major slide (in the form of a flow) occurred in March 1984 after a period of heavy rainfall	The crest of the slope was fill material. The failure occurred in the bench and resulted in disaggregation of the fill material which then developed into a debris flow¹⁴	1
Fort Canning	1984	40 m	34°	Occurred in Fort Canning Park during heavy rain in March 1984. The failure surface was shallow, about 3 m below the ground surface, but about 1500 m² of the slope started to move. Ground anchors were used to stabilise the slope	Residual soils (Grade VI) formed from the sedimentary Jurong formation	1
Gillman Heights	1985	17 m	34°	A cut slope for the Ayer Rajah Expressway at Gillman Heights showed signs of instability in December 1985. The slope was stabilised using soil nails	Medium dense to dense residual soils (Grade IV and V) derived from the sedimentary rocks of the Jurong formation	1
Admiralty Road	1987			A road cutting. The slope had been recently cut and graded during road widening. The initial failure occurred during a nine day wet period with a total rainfall of 413 mm. The slope failed in five places, two of which involved the whole length of the slope. The slope was regraded but failed repeatedly, each time after a period of heavy rainfall	Fill material of weathered granite overlying deeply weathered in-situ granite	6
Lorong Terigu		24 m	27°	This is part of the cut slopes formed during the construction of the Bukit Timah Diversion Canal. Since construction in the early 1970s a number of slips have occurred along the canal length with Lorong Terigu being the largest. The slip surface was found to be 5 to 6 m below ground surface at its deepest point	Loose to medium dense clayey silt near the surface, becoming very dense below 25 m. Standard Penetration Test (SPT) values varied from less than 10 near the surface to over 50 below 25 m. A weaker zone was observed at around 5 m depth	9
Central business district		17·8 m	53°	A number of slope failures occurred during the construction of a substantial excavation site in the central business district in Singapore. This was the highest slope to fail	Weathered sandstones and shales of the Jurong formation (Rimau facies). Degree of weathering changed from highly to slightly weathered within the top 10 m. The strata dipped steeply back into the slopes. The shale had softened during heavy rainfall	10
Bukit Batok/ Bukit Gombak	1989	40 m	27°	A cut slope at the Bukit Batok sports complex that failed after heavy rain. A backscar of 4 to 6 m was formed by the slide and about 100 m of slope was affected. The slide was 56 m from toe to crest and the maximum depth to the failure surface was 8·5 m. There was continuous rainfall for three days prior to the failure (151 mm in total), but the slope failed about 24 h after the rain stopped. There had also been an exceptionally heavy day of rain (112 mm) 19 days earlier. Water was seen to be flowing out of the slope after failure. Further shallow slides occurred in December 1991 and drainage works were implemented to stabilise the slope¹⁵	The ground conditions comprised highly weathered rock of the Gombak Norite formation. The residual soil of highly decomposed granite consisted of clayey silt with boulders	11