Evaluation of Slow-Releasing Energy Material (SREMA) Injection for In-Situ Rock Breaking Under Uniaxial and Triaxial Loading: An Experimental Study

Abstract

Permeability enhancement of impervious rock formations is crucial for the exploitation of ore deposits, which are uneconomic using conventional mining methods. These deposits have the potential to be mined with in-situ recovery (ISR) mining methods, provided the deposit’s permeability is enhanced artificially. Slow-releasing energy material (SREMA) has been identified as a promising preconditioning technique to enhance rock permeability for ISR. However, the fracturing potential of SREMA in the presence of in-situ stresses remains under-explored in laboratory experimental research studies and needs to be assessed in detail prior to field trials. A unique confining cell was developed in this study to represent realistic confining stresses underground, and the impacts of different stress conditions on the fracturing potential of SREMA were investigated. In addition, the effects of SREMA expansion in pre-existing joints were also assessed using laboratory fracturing experiments conducted by injecting SREMA into sandstone specimens with artificially created horizontal persistent joints, which is the first attempt to the best of the author’s knowledge. Under uniaxial stress conditions (10 MPa), multiple radial cracks emerged from the borehole at the centre of the specimen, while vertical splitting of the specimen was observed due to the outward expansion of SREMA inside the joint. In comparison, under triaxial confinement (5 MPa and 10 MPa), a decrease in the damage caused to the rock mass due to the expansive pressure generated by SREMA was observed, and this was overcome by introducing multiple injection holes and stress relief holes into the rock mass.