Damage constitutive model of gas-bearing coal using industrial CT scanning technology

Abstract

Determining the deformation characteristics and mechanical behavior of gas-bearing coal is beneficial to understanding the phenomena and rules of dynamic disasters during coal mining. In this study, a computed tomography (CT) scanner and a triaxial loading seepage system were used to perform CT scanning tests on gas-bearing coal under triaxial compressive conditions. We processed the CT images in different deformation stages of the gas-bearing coal and analyzed them with a digital image processing technology to depict dynamic evolution damage trend. In addition, we employed a fracture area projection method to propose a new damage variable and theoretically constructed a new damage constitutive model. The results showed that the coal specimens became prone to increased instability and damage as gas pressure increased. The growth and expansion of fissures in gas-bearing coal were heterogeneous and anisotropic and mainly experienced three processes, that is, closure in the compaction stage and elasticity stage, expansion in the strain-hardening stage, and sharp propagation and interconnection in the post-peak stage. With the progression of fracture propagation, the degree of damage gradually decreased then increased. The proposed new damage variable was more suitable than the traditional damage variable for depicting the damage degree and damage evolution process. Furthermore, the proposed new damage constitutive model well mirrored the deformation behavior of gas-bearing coal under triaxial compressive loads.