Liu Honglei

Numerical analysis on nonlinear deformation behavior of rock considering compaction of pores

The nonlinear behavior of porous or fractured rocks plays an important role for analyzing the mechanical response and stability in many geological and geotechnical applications. A stress-strain relationship considering the porosity is established for modeling the nonlinear deformation. In the present paper, firstly, on the basis of nonlinear deformation mechanism of porous or fractured rocks, the typical stress-strain curve was divided into two parts factitiously. Then, two constitutive models were established for the two parts, respectively. In order to describe the effect of the change of porosity on deformation behavior of rock, a new microcracks closure factors D ϕ was proposed in the microcracks closure phase. For the other part, elastic damage mechanics is used to describe the constitutive law of meso-level elements, the maximum tensile strain criterion as well as the Mohr-Coulomb criterion is utilized as the damage threshold. The proposed model is implemented using finite element method by MATLAB programming under the environment of COMSOL Multiphysics. Then the model was validated by comparing the numerical simulations with our experimental result and the previously published experimental data. At last, numerical simulation on failure process of 6 rock specimens with different porosities but same rock matrix under uniaxial compression is presented. It is found that the established model accurately reproduces the typical stress-strain curve, the microcracks closure phase, especially. With the increase of porosity, the uniaxial compressive strength (UCS) decreases. And the elasticity modulus increases with the porosity decrease.