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Title: Performance of repaired slope using a GEONET or GEOPIPE drain to lower ground-water table
Authors: Tan, S.-A. 
Chew, S.-H. 
Karunaratne, G.-P. 
Wong, S.-F.
Issue Date: 2000
Citation: Tan, S.-A.,Chew, S.-H.,Karunaratne, G.-P.,Wong, S.-F. (2000). Performance of repaired slope using a GEONET or GEOPIPE drain to lower ground-water table. ASTM Special Technical Publication (1390) : 3-14. ScholarBank@NUS Repository.
Abstract: A 70 m long by 5 m high slope with gradient of I(V):2(H) was cut into a medium-stiff residual soil of undrained shear strength better than 60 kPa, with drained strength parameters of about c′ = 10 kPa, and φ′ = 22°, to form the bank for an effluent pond used for irrigation of a racetrack turfing. Both drained and undrained slope stability analysis indicates stable slopes under reasonable groundwater (GW) levels expected in the cut slope. However, after a period of intense rainfall during construction, the slope suffered a shallow slip of about 1 m to 1.5 m depth over a 30 m stretch of the slope length with a vertical scarp near the top of the cut slope. This paper examines the causes of slope failure, and the strategy adopted for a permanent repair of the slope by providing internal geosynthetic drains beneath the re-compacted slope, using either a GEONET or closely spaced geo-pipe inclusions in the slope. For design, the GEONET or geo-pipe drains used must have adequate factored transmissivity to conduct expected heavy rainfall infiltration water safely out of the slope mass. Under a steady-state very heavy rainfall condition of 150 mm/h on the racetrack, it is demonstrated by the Finite Element Method (FEM) analysis, that GEONET must be provided to at least as far back as the mid-depth of the slope (about 4 m depth) to produce sufficient GW lowering to give stable slopes. The construction method of the slope repair to avoid further failure is described briefly, and the performance of the sub-soil drains in enhancing slope stability is demonstrated in the field project.
Source Title: ASTM Special Technical Publication
ISSN: 10403094
Appears in Collections:Staff Publications

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