Permeability-stress Coupling Constitutive Model Of Anisotropic Soft Rock

The constitutive theory of the soil materials is the foundation of the modern soil mechanics, the key of what is called the advanced numerical analysis method is the simulation of constitutive response for soil in fact. It is significant to establish the constitutive model correctly and apply it logically for the calculation precision. The most important to study the coupling of seepage and the stress is that the constitutive model of soil materials. Limited by the stage of the test means and theory development, there are few reports on the constitutive model of soil material considering the coupling of seepage and stress. On the background of anisotropic seepage and stress coulpling in Geotechnique Engineering project, and based on the anlysis of the constitutive model theory and its research current status, integrating the seepage and stress coupling experiment results of soft rock, anisotropic seepage and stress coupling constitutive model of the soft rock is established.The main works and the achievements of the thesis are listed as the followings.(1) Based on the modified Cambridge model, using general plastic predictiontheory, the different assignment proportion coefficient dλ₁ and dλ₂ respectively corresponding to the body stress and shear stress are introduced, whose value are determined respectively by the isotropic compression and expand curve and the shear test yield curve, a new elastic-plastic constitutive model, which is applicable to soft rock, is established. The concrete formula of the relation between stress and strain of the model in this paper is presented, and the stress-strain stiffness matrix in plane strain and axial symmetry condition is provided. The model is proved reasonable by comparing the predicted results of improved model with the Cambridge model by using a test example with the typical stress path.(2) The new concepts of reference flexibility matrix and corresponding stress state are introduced. Based on the method of matrix transformation, a new method to express the flexibility matrix (or stiffness matrix) of anisotropic constitutive model of soil is proposed. Then the anisotropic material can be transformed to the isotropic material to be analyzed, and isotropy strength theory can be applied on the anisotropic...