Results of piezocone penetration tests (CPTUs) were used to evaluate the state of consolidation of clay and the densification of sand at a reclamation site. Both the cone resistance and the penetration pore pressure from CPTU were used to estimate the vertical yield stress and strength of the consolidating clay based on the modified Cam clay model. The values of overconsolidation ratio and undrained shear strength estimated from CPTU results in clay were found comparable to those deduced from laboratory tests, in-situ pore pressure measurements, and/or field vane tests. The cone resistance was also used to evaluate the relative density and the modulus of sandfill using empirical correlations derived from in-situ density tests and conepressuremeter tests. The predicted relative density of sand from the cone resistance was found to be agree reasonably with the direct density measurement. The shear modulus of densified sandfill can also be evaluated by the cone resistance; however, the shear modulus of freshly deposited sandfill cannot be correlated with the cone resistance.
Existing reclaimed land forms a significant part of the total landspace in Singapore. Reclaimed sites in Singapore are usually underlain by hydraulic sandfill and thick layers of soft to medium firm marine clay. The hydraulic sandfill is often loose to medium dense and is usually heterogeneous due to the nature of the filling process. Densification of sandfill and improvement of the soft clay are often needed before structures or other facilities can be constructed. Evaluation of the state of consolidation in the clay and the extent of densification of the sandfill is critical in a soil improvement project at a reclamation land. This paper describes the use of the piezocone test (CPTU) for evaluating the extent of soil improvement at a reclamation site in Singapore.