The Force Chain and Acoustic Emission Response Law for the Uniaxial Compression of Rock

Abstract

The study of the force chains and acoustic emission response laws of rock masses are of major significance for the prediction and prevention of stope dynamic disasters. In the present study, the response law of the force chains and acoustic emissions of rock specimens were examined using numerical simulation and laboratory testing based on the theory of moment tensor, along with the macro–mesoscopic damage characteristics and the evolution laws of force chains and acoustic emissions. The research results indicated that under axial stress conditions, the strong chains inside rock material were distributed in “root-like” shapes, and the direction of the strong chains had been controlled by the directions of the stress loading. The number of internal force chains and their intensities during the loading of the rock material were found to be negatively correlated. The root causes of the formations and expansions of the fissures in the rock material lies were found to be related to the fractures and instability of the strong chains on both sides of the fracture surfaces. It was determined in this study that the corresponding acoustic emission responses of the examined rock specimens under the conditions of uniaxial compression could be divided into five phases as follows: a weak phase; stable phase; stable enhancement phase; sharp enhancement phase; and peak phase. The phases indicated the spatial distribution shapes and intensities of the acoustic emissions during each stage. The force chains, fissures, and acoustic emissions in the rock material were found to be synchronous in time, spatially homogeneous, and consistent in intensity. The results of this study revealed that the mechanical nature of the fissures and acoustic emissions in the rock specimens were caused by the transferences, transformations, fracturing, and reconstructions of the internal force chains of the material after external force had been exerted. The energy released as a result of the instability of the force chains had led to instability deviations of the coal rock particles, which had subsequently caused damages to the force chains. As the rock material became increasingly damaged, meso-fissures had been formed. Also, part of the unabsorbed energy was released to form acoustic emission phenomena.