Underground Singapore 2011 The reclamation material was placed about 30 years ago consisting of excavated old alluvium soils from Bedok area in the eastern part of Singapore. The moisture content of samples collected from reclamation fill ranges from 10% to 60% indicating mixed sandy and clayey materials. The unit weight varied from 16 to 22 kN/m3. The fill material is typically classified as silty sand (SM) and clayey sand (SC) under the British Soil Classification System. The fines content varying from 5% to 80% is plotted against elevation in Figure 2a. The Atterberg Limits from samples with high fines content are plotted in Figure 2b. Some samples are located close to A-line and can be classified as intermediate to highly plastic inorganic clays. The Kallang Formation comprises of very soft upper marine clay, lower marine clay, loose fluvial sand, peaty estuarine deposits and occasionally a stiff clay layer. The Old Alluvium is an alluvial deposit that has been variably cemented and weathered. The OA deposits are non-uniform and can be classified as clayey sand, silty sand, silty clay or clayey silt for engineering purposes. The SPT N values for OA layer ranges from 3 to more than 100 depending on the cementation, weathering grade and composition of the soil. The OA soils in Singapore are classified under 5 different weathering grades: A to E, with A indicating unweathered and E being completely weathered as a residual soil.
Figure 1 CPT field test results at the site.
Figure 2 Fill material fine content and plasticity
86