Effect of sampling disturbance on properties of Singapore clay

Abstract

This paper examines results from triaxial unconfined compression tests and undrained compression tests on reconsolidated samples of a Singapore marine clay retrieved using two sampling methods that offer differing quality of samples. Both local internal strain measurements using a Hall-effect transducer and external strain measurements using LVDTs were employed in the triaxial tests. Bender elements were embedded in some of the samples to establish the maximum shear modulus. If the samples are not reconsolidated, the shear strength and stiffness determined from triaxial tests are found to be sensitive to the quality of the samples, and generally lower than that determined by in situ tests. However, if the samples are subjected to isotropic or Ko consolidation to the estimated in situ condition, there is little difference between the shear strengths of samples retrieved using different samplers, and also consistent with results from vane shear tests. However, for the maximum shear modulus, even with reconsolidation, there is still a 10% difference between the results from samples retrieved using different samplers. Further, the laboratory determined maximum shear moduli are about 10% lower than the value determined in an in situ seismic cone test.