Spalling characteristics of sandstone containing rectangle hole with gradient cavity height: An experimental and DEM numerical study

Abstract

Spalling failure commonly exists during the progressive excavation of underground engineering, and the stepped excavation of underground mining stope is rarely simulated in previous studies. Therefore, the biaxial compression test is finished by sandstone samples containing rectangular hole (with different cavity heights), and the corresponding numerical simulation is conducted by the discrete element method. Based on the mechanical, optical and acoustic data captured during the test, the main results and conclusions are as follows: 1) There are two paths to activate the typical spalling failure, the first way is caused by the rapid energy release (manifested as sudden AE burst), and the second way is that the released energy accumulates to a threshold over a long period and finally causes large-scale damage. 2) The relatively larger cavity height delayed the initiation of central tensile failure in the roof & bottom surrounding rocks and the spalling failure in sidewalls. 3) The relatively larger confining pressure contributes to the early construction of the spalling failure and limits the extension of the central tensile crack bands. 4) The construction of spalling failure is very fast, the ejected rock plates are caused by several rounds of spalling failure, and the final V-shaped groove is built by the spalling failure and internal crushing failure.