A Study on the Permeability and Damage Characteristics of Limestone under Stress–Seepage Coupling Conditions

With the increase in energy demand, energy engineering has gradually developed to go deeper, accompanied by a complex geological environment, such as the coupling of stress and seepage. Limestone is widely found in underground rock engineering, and its stress–seepage coupling characteristics have a great influence on the safety and stability of related engineering projects. In order to study the permeability characteristics and damage evolution of limestone during the deformation and failure process under stress–seepage coupling conditions, permeability and acoustic emission tests on limestone were performed in this paper. The results showed that: the stress–strain curve demonstrated periodicity, as did the permeability change. The change in permeability in different deformation stages of axial strain and lateral strain was similar, but it was more appropriate to reflect the permeability evolution in terms of lateral strain. The permeability of the limestone slightly decreased in the volumetric compression stage, and tended to saturate after a sudden increase in the expansion stage. The presence of the confining pressure reduced the permeability of the rock. In the process of limestone deformation and failure, the level of acoustic emission activity can reflect the degree of fracture development. The permeability characteristics and acoustic emission characteristics had a good corresponding relationship. The greater the confining pressure, the higher the acoustic emission activity. The deformation and damage process of limestone experienced three stages: damage stable growth, damage acceleration development, and damage saturation.