EFFECT OF CURING STRESS AND PERIOD ON THE MECHANICAL PROPERTIES OF CEMENT-MIXED SAND

摘要

Cement mixing is one of the popular ground improvement technologies in geotechnical engineering practice. In order to effectively and confidently design cement-mixed soil structures for specific purposes, its stress-strain behavior needs to be well understood. Though there have been many studies on cement-mixed soils using different types of soils, their behaviors have not been generalized yet. As is the case with concrete materials, the hydration of cement in cement-mixed soil continues with time, thereby improving the strength and deformation characteristics of cement-mixed soil over time. In the field, the cementation bonds are formed under stress in case of in-situ soil. However, in the usual testing techniques, cementation bonds under stress has not been a point of consideration in most of the previous studies. This has led to an underestimation of the stress-strain behavior of cement-mixed soil. On the other hand, soils are subjected to confining stress during loading which has also some effect on the strength and deformation characteristics of soil which has not been considered yet in the case of cement-mixed sand. This study investigates the effect of curing stress and period on the strength and deformation characteristics of cement-mixed sand. The effect of confining stress in the triaxial test is also investigated in another series of specimens. A series of consolidated drained (CD) triaxi-al compression (TC) tests were done along with the small strain cyclic loading and bender element tests during mono-tonic loading to determine the small strain Young's modulus (Ev) and shear modulus (Gvh) respectively. The effect of the curing period is significant in the peak strength, stiffness, Ev, Gvh and also in the post peak regime. The curing stress also has a significant effect on the peak strength, Ev and Gvh. The confining stress has an effect on the peak strength, stiffness and in the post peak regime. However, the effect is small compared to clean sand.