Investigation on Dynamical Mechanics of Rock-Backfill Composite Samples under SHPB Test

Abstract

In blast-induced caving mining employing backfilling techniques, understanding the mechanism of interaction and evolution of deformation between rock and backfill under coupled conditions has become essential. In order to perform dynamic uniaxial impact testing at high strain rates utilizing the Split Hopkinson Pressure Bar (SHPB) test technique, this research produced coupled specimens of rock and cemented tailing backfill (CTB). The coupled body's stress-strain curves at various strain rates were measured, and the failure processes behind them were examined. Using GDEM software, a coupled model of SHPB rock-CTB was created in order to examine the internal variations in stress wave velocity as well as the evolution of cracks in the coupled specimens. According to experimental results, the dynamic compressive strength of the connected body increases first, falls later, and finally stabilizes when the average strain rate (ASR) increases from 27.45 s− 1 to 68.73 s− 1. At typical strain rates below 60 s− 1, the stress-strain curve displays a "stress drop" type, and at rates over 60 s− 1, a "stress rebound" type. When the ASR is below 55 s− 1, the energy absorption progressively increases; when it is above 55 s− 1, it reduces and then increases again. The simulation results validate the validity of the experimental conclusions by showing that transverse and longitudinal cracks occur on the surface of the backfill, with greater deformation observed on the side in contact with the transmission bar compared to the side in contact with the rock.