Behavior of soft singapore marine clay treated with cement

Abstract

The strength and deformation characteristics of soft Singapore marine clay are evaluated through a series of unconfined compression, oedometer consolidation and consolidated undrained triaxial compression tests. The results show that the unconfined compressive strength as well as the stiffness of the treated clay increases with cement content and curing time. Local strain measurement using Hall's effect transducer enables the accurate determination of the true stiffness of the cemented clay at very low strain level as compared to the conventional method of external strain measurement. Based on the rate of strength development, the unconfined compressive strength and cement content relationship can be divided into 3 zones: Inactive Zone, Active Zone and Inert Zone. The addition of 30% cement content changes the soft and ductile clay material to a more brittle material, while adding less than 30% cement the marine clay remains a ductile material. The significant increase in apparent pre-consolidation pressure and reduction in apparent compression index are observed from oedometer consolidation tests of cement treated clay samples at in-situ stress range. The e-logav relation of cement treated clay at stresses beyond the apparent pre-consolidation pressure is almost parallel to the virgin consolidation line (VCL) of the untreated soft clay and destruction of the cementation effect of treated clay incurs. The ly-logo'v plot renders the confirmation of hardening effect and overconsolidated behavior by the inclusion of cement in soft clays. The cement treated samples show very small positive excess pore pressure development in triaxial undrained tests during the shearing stage at normal in-situ stress range. It is found that the behavior of cement treated Singapore marine clay is very similar to the overconsolidated clay. Thus, the remarkable improvement of strength and deformation properties of soft Singapore marine clay treated with cement indicates that the mechanical cement mixing method or jet grouting method can be an effective soil improvement technique for construction in soft clay.