Damage characteristics analysis and constitutive model establishment for deep rock considering pre-static loads and frequent dynamic disturbance

In order to characterize the mechanical behaviors of deep rock mass in complex geological environments, a statistical damage constitutive model was established according to the element combination method. In this model, the effects of pre-static loads and frequent dynamic disturbance on the mechanical and statistical parameters of rock were considered and a new function was introduced to deduce the damage evolution equation. This model was then verified against relevant test and literature data. The results show that the damage evolution rate curve gradually moves to the right along the strain axis and the peak value of the curve decreases first and then increases with the increase of parameter k related to the disturbance number. When k is large, the damage evolution rate curve appears a 'platform'. This platform may correspond to the stable development stage of damage. Besides, pre-static loads can improve the impact resistance of rock. The energy release in the rebound stage under pre-static loads is higher than that without pre-static loads when the disturbance number is constant. The energy release and impact resistance of rock decrease with the increase of disturbance number if the pre-static loads remain unchanged. The proposed model can better describe the mechanical properties and stress–strain behaviors of rock under the combination of pre-static loads and frequent dynamic disturbance. For the rebound type curve, its predictions are very consistent with test data in the pre-peak stage; For the strain-softening type curve, it does not only well with test data in the pre-peak stage but also has high fitting accuracy in the post-peak stage. This study can provide beneficial reference for the evaluation of the safety and stability of deep rock engineering.