Influence of high water pressure on dynamic energy dissipation and failure characteristics of rock

Underground engineering rock mass is generally in water pressure and ground stress environment, resulting in water inrush and other accidents, which seriously restricts the safety and stability of underground engineering. In order to study the influence of water pressure and ground stress on the energy dissipation and failure characteristics of rocks, the dynamic test system of rocks with high water pressure and high ground stress was independently developed, and multiple groups of water pressure and axial static stress were set to simulate the groundwater pressure and ground stress environment to carry out impact tests on rocks. The dissipated energy of rock is calculated based on the incident wave, reflected wave and transmitted wave, and the relationship between the energy dissipation rate of rock and the water pressure and the axial static stress is studied. The rock specimen after impact is screened and its mass fractal dimension is calculated, which is used to characterize the damage degree of the rock specimen and study the influence of water pressure and axial static stress on the fractal dimension of rock. The pore-emanated crack model was improved to study the variation rule of rock microcrack growth and explore the influence mechanism of water pressure and axial static stress on rock failure characteristics. The results show that the energy dissipation rate of rock increases first and then decreases with the increase of water pressure, which indicates that the increase of water pressure first promotes and then inhibits the energy absorption of rock. The energy dissipation rate continues to increase with the increase of axial static stress, indicating that increasing axial pressure is conducive to enhancing the energy utilization rate of rock. Under the same coaxial static stress condition, the fractal dimension of rock mass decreases with the increase of water pressure, that is, the damage degree decreases continuously. Under the same water pressure, the fractal dimension of mass increases gradually with the increase of axial static stress, that is, the damage degree increases gradually. The improved pore-emanated crack model can directly characterize the effect of water pressure on microcrack growth. The increase of water pressure inhibits the growth of dynamic microcracks and decreases the macroscopic failure degree of rock.