Study Of Mechanical Properties And Constitutive Model On Undisturbed K₀Consolidation Clay Of Hong Kong-Zhuhai-Macao Area

Soft clays are widely distributed near the littoral in southeast China and it brought many difficulties to the engineering because of the high water content, poor permeability, low strength and strong deformation. It may be give the engineering to bring problems or even disasters due to lack of awareness of the certain structural and anisotropy of the natural clay. By laboratory experiments to obtain the mechanical properties of clay is the common method, this article studies on the mechanical properties of the undisturbed clay of the Hong Kong-Zhuhai-Macao by K0consolidation undrained triaxial compression tests, using appropriate constitutive model to fit the test results which the parameters of the model obtained by the experiments.First, the coefficient of earth pressure at rest K0is studied on by the K0consolidation tests of the undisturbed saturated samples of Hong Kong-Zhuhai-Macao clay. The changes of Ko under different loading and unloading paths are studied, the applicability of using common formula and recommended value to estimate the K0is analyzed, the prediction equation based on the test results is given, and the test results showed that the K0of mud/silt clay could be0.47, the K0of silty clay is between0.30and0.45. The K0coefficient of undisturbed is significantly lower than the K0coefficient of remodeling samples by contrast with the K0coefficient of the clay of this region.Secondly, the mechanical characteristics of the undisturbed clay of Hong Kong-Zhuhai-Macao after the test of Ko consolidation undrained triaxial compression are studied. The initial water content, dry density, structural yield stress and soil heterogeneity will affect the shear strength of clay after analysis of test results. When consolidation stress is much greater than structural yield stress, the structure of the soil has been damaged, structural disappeared and the ratio of shear strength and consolidation stress is between0.278and0.328, we could also use empirical formula to calculate the ratio of shear strength and consolidation stress of overconsolidated clay by the ratio of normal consolidated clay. Comparison of the compression test results of Ko consolidation and isotropic consolidation, we found that undisturbed clays with structural exhibit softening behavior and remolded clays showed hardening characteristics and the methods of consolidation have little effect on critical state stress ratio and effective internal friction angle. Finally, according to the constitutive equation of modified Cambridge model and S-Clayl model which the parameters obtained from the tests, we simulate the process of undrainded triaxial compress. The model can better simulate the remodeling soil test results but there is a certain gap between the calculated results and test results when we contrast the calculated results and test results, needing to consider the impact of structural on stress-strain relationship and new parameters should be introduced to improve and perfect of the model.