INTRODUCTION:

The soft Singapore marine clay is well noted for its low shear strength and high compressibility. Thus, deep cement mixing and cement jet grouting has recently been used to improve the strength and deformation characteristics of this soft clay. A comprehensive laboratory testing program was carried out on the effect of inclusion of cement on physical and engineering behaviour of soft Singapore marine clay. Series of unconfined compression and oedometer consolidation tests were conducted with cement content varies from 5 % to 30% and having curing periods of 7 days and 28 days. Cement slurry with water-cement ratio 1.0 was used and the resulting total initial water content was 90% and 120%. Test results showed that increase of cement content and curing time reduced the water content of the final hardened cemented clay and the plasticity of the treated clay. The increase of cement content and curing time exhibited significant improvement of unconfined compressive strength as well as stiffness of the treated clay. Local strain of the cemented clay was also measured using Hall's effect transducer as a comparison to the conventional method of external strain measurement. The oedometer test results revealed that the consolidation properties improved significantly with increasing cement content and curing time. Due to the addition of cement, the apparent increase in preconsolidation pressure and reduction in apparent swelling index were realised. Test results also showed that the (e-logsv') relation of cement treated clay at higher stresses was almost parallel to the virgin consolidation line (VCL) of the untreated soft clay. 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.

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