A damage-based analytical model to evaluate seepage pressure effect on rock macro mechanical behaviors from the perspective of micro-fracture

The deterioration of rock material properties induced by seepage pressure is a serious danger to the stability of geotechnical engineering. The formation and propagation of microcracks is the primary cause of rock macro failure. This work proposes an damage-based analytical model to assess the impact of seepage pressure on the macro mechanical behaviors of rocks from the standpoint of micro fracture. A wing crack model serves as the foundation for the analytical model. This model has taken into account the impact of seepage pressure on the initiation and growth of wing cracks. The constitutive relation is constructed based on the equivalency connection of damage defined by strain and wing crack length. A comparison between the analytical results and the reported experimental data confirms the reasonableness of the analytical model. Investigations are conducted on the relationship between the macro mechanical behavior of rocks and micro fracture under various seepage pressures, confining pressures, and microscopic parameters. The findings demonstrate that the cracks growth is initially steady before becoming unstable. The growing process of wing cracks stops when they connect with one another, and friction between the crack surfaces takes over. The initiation and growth of wing cracks may be aided by the seepage pressure. As the wing crack propagates, the seepage pressure effect initially increases, then decreases, and eventually has practically no impact. The influence of seepage pressure on rock macro mechanical behavior is that with seepage pressure increasing, the initiation stress and peak stress decrease, but the residual stress is basically a constant. The rock micro fracture process is significantly influenced by confining pressures and microscopic factors, which in turn affect the macro mechanical behavior. The study’s findings offer a micro fracture foundation for comprehending how seepage pressure affects the macro mechanical behaviors of rocks.