Experimental investigation on mechanical, acoustic, and fracture behaviors and the energy evolution of sandstone containing non-penetrating horizontal fissures

Abstract

Flaws are the weakest part of rock mass, which directly determine the stability of underground engineering. Existing investigations on the mechanical behaviors of flawed rock mainly emphasize on the geometric parameters of the fissure, such as inclination, width, and length, but few works have been conducted on the effect of fissure location on rock properties. This study explores the influences of two fissure layouts (distance between horizontal single fissure and specimen end, and horizontal double fissures spacing) on the sandstone properties under uniaxial compression. The properties studied include strength and deformation, failure mode, acoustic emission (AE) characteristics, and energy evolution. The findings indicated that pre-existing fissures significantly reduced the rock's strength, elastic modulus, and peak strain, and the rock's mechanical properties decreased as the distance between the horizontal single fissure and the specimen end decreased and as the double fissures spacing increased. Furthermore, it was observed that intact specimens mainly underwent shear failure and the flawed rocks under uniaxial compression experienced splitting failure or both. The flawed specimens presented multiple higher AE counts before the peak stress, corresponding to crack initiation, propagation and coalescence, which were distinctly distinct from the intact specimen. The energy evolution characteristics of the fissured sandstone reflected their damage process. The findings are promising to improve the understanding of mechanical mechanisms and energy evolution of flawed rock engineering.