Water is a scarce and important resource in Singapore. One technique involved in increasing the availability of this natural resource is to draw water from major water channels that are located within water catchment areas into abstraction ponds. These abstraction ponds usually cater a storage capacity of between 50,000 m~3 and 100,000 m~3. This paper describes the design, construction and field observations of T-shaped diaphragm walls that were utilized as a retaining system to enclose an abstraction pond, which has a maximum depth of about 12 metres. The T-shaped diaphragm wall was preferred over a conventional rectangular diaphragm wall, as lateral bracings were not provided to shore the retaining structure in unfavorable ground conditions, in order to satisfy the requirement of a totally obstruction-free pond. The top 15 metres of the ground consists of thick, soft and loose backfill soils, which have low strengths and stiffnesses that could lead to large wall movements and undesirable stresses in a conventional rectangular diaphragm wall. The geometry of the T-shaped diaphragm wall retaining system was 1-metre thick, with 1.8-metre long fin sections that are spaced at 4 metres apart. The walls were designed as a 12-metre high cantilever system, which are socketed into dense and very dense sandy/clayey silt soils. The ground deformations and wall movements were closely monitored through ground instrumentation. This paper also presents a comparison between the results obtained from finite element analyses and measured field data.
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