Dynamic damage mechanism of coal with high true triaxial stress level subject to water jets

Abstract

Deep mineral resources are abundant, and water jet technology has been proven to be an efficient means of developing this resource. In-situ stress is one of the prominent features in deep mines. However, the dynamic damage process of rock under the in-situ stress environment subject to water jets has not been revealed. Therefore, this study aims to fill this gap. For this study, coal breaking tests were performed to reveal the macro fracture patterns of coal under different true triaxial stress conditions. The results show that the bedding angle can significantly affect the coal-breaking characteristics, and when the bedding angle is 45° combines the advantages of length and aperture for jet drilling. When there is no geostress, the width of the cracks on the wall of the fracture pit is 3 μm, with a crack width of 7.5 μm at the bottom of the hole, and no through cracks generated under triaxial stress. Subsequently, further theoretical analysis and numerical simulation showed that the in-situ stress has a hysteresis and inhibitory effect on the dynamic damage evolution of jet coal breaking, hereby affecting the final fracture mode during the period. The results of this study will provide basic theoretical support for the jet drilling of rock in deep layered rock.