Study on mechanics and damage characteristics of sandstone under cyclic impact state

In order to study the mechanics and damage characteristics of sandstone under cyclic impact state, a separate Hopkinson pressure bar test device is used to carry out cyclic impact tests on red sandstone with different incident amplitudes.The damage evolution law of red sandstone is analyzed by Weibull distribution statistical damage model.The research results show that when the cyclic impact test is carried out with an incident stress of 90 MPa, as the number of cyclic impacts increases, the dynamic strength first increases and then decreases.The maximum strain and the average strain rate first increase and then decrease.The first impact helps to improve compressive strength of red sandstone.As the incident amplitude increases, the incident stress is impacted at 100 MPa, 110 MPa, and 120 MPa, the dynamic strength, deformation modulus and cycle times gradually decrease, and the maximum strain and average strain rate gradually increase, the damage model based on Weibull distribution can reflect the damage evolution characteristics of this material.The cumulative damage increases with the increase of the number of impacts.The cumulative unit volume absorbed energy has good consistency with the cumulative damage law, and the rock sample appears when the instability failure is large, the cumulative damage is around 0.8, and there is no obvious change.The research results provide a theoretical basis for the safety protection of mine rock masses and the correct evaluation of rock stability.