Constitutive Model Of Structured Clays And Study Of Parameter Determination

The problem of constitutive model of structured soils is the focus problem of soil mechanics in the 2l century. This paper deals with the ccnstitutive model of structured clays. During the last three decades, many constitutive model for clay have been proposed and studied. The most important may be the Cam clay model which was originally developed for remould clay and based on experimental results for remould Weald ay. But natural soil usually have their pecuilar stucture and their behavior can not be properly modeled by traditional elasto-plastic theory. From an engineering point of view, the need for a natural clay model, which can accurately predict the behavior of soft clay deposited with the increased construction activity in recent years, has become more urgent. In this study, a structured clay is regarded as an assembly of lumps of different sizes, and it is assumed that the total deformation consists of three parts, i.e. elastic deformation of lumps, plastic deformation due to sliding between lumps and irrecoverable deformation due to crushing of lumps. Usually yield function is introduced to describe the plastic deformation, damage function is proposed to describe the deformation due to the damage of soil structure. In order to link the micromechanics to macroscopic behaviour of clays and to establish structured clay constitutive model, the plastic yield function and damage function have been researched by microstructural sliding model and microstructural crushing model. A study is made of rheology of clay which is assumed to obey the worknet theory of polymer and rate process theory. The theoretical predictions are found to agree with experimental results. The studies theoretically support the masonry model for structured clays proposed by Zhujiang Shen. Based on the masonry model, a viscous-elastic-plastic model for structured clays has been proposed, it is assumed that the total viscous deformation consists sliding viscous deformation and damage viscous deformation. It is shown by the simulation that the model can well duplicate the rheological properties of structured clays. By putting some amount of cement and ice particles in soil samples, structured clay with macropores is prepared. Then, on structured clays and the remoulded clays the virgin compression test, CD tests and CU tests with different strain-rate have been carried out to clarify the strength-deformation characteristics and to determine the strain-rate effect and yielding characteristics. In addition, CPTU test on structured soil with different installation rate have been carried out. On the basis of nonlinear continuum mechanics, the Total Lagrange method is used to develop an FEM consolidation analysis program for large-strain analysis. The effect of rigidity rotation constant is observed while the model presented in this paper is used in constitutive laws. The simulations of CPTU test have been successfully performed, and the parameter q0 has been derived from CPTU test by simulating inversion method.