Numerical analysis of borehole parameters effects on strength weakening of red sandstone

Abstract

In addition to the high stress, hard rocks around deep mine entries are also subject to the disturbed stress by mining activities nearby, which increases the risk of rockburst incidents. One preventative measure is the employment of drilling pressure relief (DPR) on hard rocks. This paper analyzes the borehole parameters effects on strength weakening of red sandstone through numerical simulation based on the finite difference method. Input parameters for the numerical simulation were determined by the calibration with laboratory test results. A series of uniaxial compression tests were conducted on red sandstone specimens (100 mm × 50 mm × 50 mm). The mechanical properties and strain energy characteristics of red sandstone were analyzed under different drilling schemes (borehole number, borehole diameter, borehole depth, borehole position, and borehole arrangement angle). The results show that the uniaxial compressive strength (UCS) and strain energy storage capacity of red sandstone decrease by 1.60-39.20% and 35.84-92.77%, respectively after DPR. Moreover, there is a positive correlation between the UCS and elastic strain energy. Further sensitivity analysis of borehole parameters has concluded that the UCS of the specimens is significantly affected by the number of boreholes. In contrast, the borehole diameter prominently affects the strain energy storage capacity. This study verified that DPR has a substantial strength-weakening effect on hard rock, providing a theoretical foundation for further improving the mechanism of DPR in rockburst prevention.