Abstract:

The concept of effective stress is mostly used in hydro-mechanic coupling study, while it is difficult to determine the values of Biot’s coefficients. A test system is developed to study the evolution of Biot’s coefficients in cracked rock materials induced by deviatoric stress. In the plastic deformation phase of triaxial compression test, some loading-unloading cycles of axial stress were carried out at different levels of axial strains. After injection and squeeze water into/out of the specimen at the end of axial stress unloading process, the deformation is recorded during the loading-unloading cycle of pore pressure. The Biot’s coefficients in axial and lateral directions are calculated based on the method proposed by Shao. The evolution of axial and lateral Biot’s coefficients at different levels of axial strains is presented in a series of confining stresses; it is found that: 1）the property of Biot’s coefficients is anisotropic, it is reasoned that the cracks in the specimen are grown along the direction of maximum normal stress; 2）the axial and lateral Biot’s coefficients are increased when axial strain increases, the increasing of axial strain leads to the propagation of cracks, consequently causes the Biot’s coefficients augment; 3）the values of axial and lateral Biot’s coefficients under low confining stress are greater than the one under high confining stress, the reason is that the failure style is changed with confining stress.