A gas-mechanical-damage coupling model based on TLF-SPH method to simulate gas seepage in fractured coal

Abstract

The coupled calculation of gas seepage in fractured coal is always the focus and difficulty of computational mechanics. Therefore, combined with the phase field theory, the gas seepage model of fractured coal is developed under the framework of smoothed particle hydrodynamics (SPH). The accuracy of the seepage model based on partial differential equation (PDE) with constant coefficient is verified by a reference example, and the simulation results agree well with the analytical solutions. Meanwhile, the seepage characteristics of gas in homogeneous coal based on PDE with constant and variable coefficients are analyzed, respectively, with their numerical errors compared. Then, based on the gas seepage model of fractured coal, the effects of heterogeneity, defect opening and inclination on gas seepage in coal are studied, respectively. In addition, considering the influence of coal deformation and pre-existing defects on gas seepage, a gas-mechanical-damage coupling model for gas seepage simulation of fractured coal is proposed by using SPH method with total Lagrange formula (TLF-SPH). Subsequently, the permeability evolution and gas seepage characteristics of borehole surrounding rock under different conditions (such as overburden load, extraction pressure, borehole radius and initial gas pressure) are investigated, revealing the seepage-mechanical coupling mechanism of fractured coal during gas extraction. This work provides important theoretical support for mine gas extraction and gas outburstdisaster prevention technology.