Study on the failure modes of water-bearing soft rock under different low-frequency disturbance

Abstract

To investigate the evolution of failure modes in soft rock under various low-frequency disturbances and varying moisture content, a creep impact dynamic disturbance loading system was employed. Experiments were conducted on soft rock samples with different moisture contents, while the loading process was monitored using an acoustic emission system. The fracture development and propagation characteristics were reconstructed using a CT scanning system. The experimental results reveal that: (1) The failure mode of dry soft rock transitions from “shear-tension-shear” with increasing initial disturbance, whereas water-bearing soft rock primarily undergoes tensile failure. (2) During disturbance, saturated soft rock exhibits significant fluctuations in acoustic emission characteristic parameters, with the initiation of larger fractures. As the initial disturbance increases, failure transitions from plastic to brittle, resembling the behavior of dry samples. (3) Microcracks in both dry and saturated soft rock predominantly range from 500 to 1000 µm, while those in naturally moist soft rock are less than 500 µm. Although the volume of primary fractures varies slightly among different states, the overall degree of damage increases with higher moisture content. These findings elucidate the evolution of failure modes and fracture development in soft rock under low-frequency disturbances, providing valuable insights for monitoring, early warning, and mitigation of dynamic disasters in deep mines.