Mechanical Analysis of the Coupled Gas-Solid-Thermal Model during Rock Damage

Gas fracturing technology is the key to the exploration for unconventional petroleum resources and other engineering industries, so the research on the coupled gas-solid-thermal model during rock damage has the important significance to the development of gas fracturing technology. By introducing rock damage variable, the coupled gas-solid-thermal model during rock damage is established in this paper, besides, the rock damage constitutive is written with MATLAB software, which is embedded in the multi-physics coupling software COMSOL in the process of numerical computation. Based on this, the damage rule of rock mass around drilling under high pressure gas is analyzed. The results show when the ratio between x direction local stress sigma(x) and y direction local stress sigma(y) is 1, the rock failure is dominated by shear damage due to the effect of gas; when the ratio between x direction local stress sigma(x) and y direction local stress sigma(y) is 1/10, pull damage appears on both sides of drilling in the direction of Y because of the effect of gas; with the passage of time, the pore pressure in the rock mass increases gradually, while the pressure gradient decreases gradually; the primary temperature of rock mass has little influence on the pore pressure.