Grain-based modeling study of time-dependent mechanical behavior of brittle rocks in deep underground caverns based on the stress corrosion model

Abstract

Failure and instability in deep underground caverns, such as delayed rockburst and time-dependent deformations, are not immediate after excavation. These phenomena are closely linked to the complex stress conditions affecting deformation and fracture mechanisms in brittle rock over time. Therefore, understanding the mesoscopic evolution mechanism of time-dependent deformation and fracture in brittle rocks is crucial. This study conducted single-stage loading and creep experiments on marble in the Jinping I underground powerhouse to investigate the influence of stress levels and stress-strength ratios on time-dependent deformation and fracture using grain-based and parallel-bond stress corrosion models. Results indicate that the long-term stress strength ratio is governed by stress levels. Higher confining pressures have less impact on time-dependent deformation and fracture, resulting in longer failure time or even absence of failure. Conversely, higher stress-strength ratios significantly impact brittle rock, leading to shorter failure time. Increasing confining pressure or stress-strength ratio primarily controls the micro-evolution mechanism of time-dependent fracture in marble through the interaction between tensile and shear cracks. More tensile cracks decrease the number of shear cracks. Under larger load gradients, time-dependent deformations and failure decrease, resulting in longer unstable failure time.