Stress-Strain behaviour of Cement-Stabilized Hong Kong marine deposits

Abstract

The deep cement mixing (DCM) technique is an in-situ ground improvement method to stabilize and solidify soft clay ground. To facilitate the practical design of DCM, it is necessary to establish the relationship between the strength and stiffness of cement treated soil with governing factors first. In this study, the influence of different seawater and cement contents on the strength and stiffness of cement stabilized Hong Kong marine deposits (HKMD) was investigated by a series of unconfined/confined compression tests. According to the experimental results, an attempt was made to predict the unconfined compressive strength (UCS), qu, by using a simple empirical equation based on water/cement ratio (w/c). The correlation between the strength and secant modulus of improved HKMD was obtained. Importantly, a linear relationship between small-strain (ε < 0.1%) stiffness and qu was formulated based on the measurement results from local linear variable differential transformers (LVDTs) and strain gauges. Besides, the effect of w/c on the failure mode of the specimens was revealed. In addition, the consolidated undrained (CU) triaxial tests indicated that specimens gained higher peak strength with increase of confining pressure. All the findings are of practical significance for the local ground improvement industry as well as for other coastal cities around the world.