Experimental and Numerical Investigation on the Dynamic Responses of Rock-Like Plates Containing Double Parallel Cracks Under Pre-Loads

The surrounding rock in deep rock mass engineering is often subjected to static loads and dynamic disturbances. The groups of discontinuities contained in the rock mass often affect the stability of rock mass engineering. Therefore，it is relevant to systematically study the mechanical properties and fracture behavior of multi-jointed rock masses under static-dynamic coupling loadings. The dynamic experiment of the parallel double-jointed rock material plate were conducted using the improved split Hopkinson pressure bar(SHPB)loading system under four types of axial pressures. Moreover，the SHPB discrete element numerical model’s feasibility was verified，and the hydrostatic pressure SHPB model was further established based on flexible loading. The fracture behaviors of the specimens under different pre-loads were examined. The results revealed that the specimen’s dynamic strength and total strength show rate dependence under the same axial loads；the dynamic strength of the specimen gradually decreases with the increase in the axial pre-loads under the same loading rate，whereas the total strength increases and later decreases. Under axial pre-loads，the failure mode of the specimen changes from tensile shear failure to shear failure with the increase in loading rates. In hydrostatic pressure environments，the parallel double-jointed specimen’s dynamic strength and total strength also show significant rate dependence，higher than that of the specimen under the same axial pre-loads. The specimen’s dynamic strength and total strength have a significant confining pressure enhancement effect under the same loading rates. The specimens finally showed an “X”-shaped shear failure mode，which was not significantly related to the loading rate and hydrostatic pressure，and the effect of hydrostatic pressure could significantly inhibit the generation of cracks in the tensile wings. Furthermore，the crack initiation time was affected by the loading rates，axial pre-loads，and hydrostatic pressure. © 2023 Tianjin University. All rights reserved.