Study on Dynamic Characteristics of Deep Siltstone under High Static Stress and Frequent Dynamic Disturbance

Abstract

The mechanical characteristics of siltstone under high static load and frequent dynamic disturbance were investigated by the improved split Hopkinson pressure bar (SHPB), which is used to simulate the failure phenomenon of the extracted ore drift owing to high stress concentration and blasting disturbance in Dongguashan copper mine at the depth of more than 900 m. The maximum dynamic strain, dynamic stress, and dynamic deformation modulus of rock of each impact were researched to provide theoretical basis for mining production. The results show that the dynamic stress-strain curves of siltstone before the peak stress present two characteristics of linear and nonlinear variation and different degrees of resilience after the peak stress under high static stress and frequent dynamic disturbance. The strain rate rises in a linear trend with the increasing times of dynamic disturbance, but the value of the strain rate is approximately constant in the process of one impact. With the increase of the strain rate, the maximum dynamic strain rises at the same static stress, while the peak dynamic stress and dynamic deformation modulus decrease linearly. Because the inner stored elastic energy of rock determines the value of resilient strain after unloading, the elastic energy may increase with the increase of static axial stress in a certain range and then the resilient strain increases. Accumulative times of dynamic disturbance and static axial stress show the relationship that the former is obviously reduced with the increase of the later.