Experimental research on the mechanical and acoustic emission properties of layered sandstone during tensile failure

Abstract

Bedding planes exert great influences on the mechanical properties of layered rocks. To investigate influences of properties of bedding planes on the strength, failure mode, and acoustic emission (AE) characteristics of rocks, three-point bending tests were carried out on layered sandstone containing bedding planes of different dip angles. Results show that the failure strength of the layered sandstone shows a first large decrease and then slight increase trend with the rise of the dip angle θ of bedding planes under both conventional loading and multi-block cyclic loading. According to failure characteristics of the rock, the failure can be divided into three modes: matrix failure, mixed failure, and failure of bedding planes. In addition, the damage characteristics reflected by the AE count and AE energy, RA-AF distribution characteristics, and AE source locations show consistency in the same failure mode. Influenced by the multi-block cyclic loading, the failure strength, peak deformation, damage ratio reflected by the AE count and AE count at failure, and the number of shear cracks reflected by the RA-AF distribution of rocks with bedding planes of the same dip angle all increase to different extents. Moreover, the majority of residual deformation and damage in the loading process occurs in the initial period of cyclic loading and unloading in each block. The research result represents a useful complement to the mechanics theory of layered rocks and is of important significance for ensuring the safety of rock engineering.