Rock fracturing mechanism and arrangement of fracturing holes using hydro-mechanical splitters

For more-efficient tunneling in hard rock, reported here are simulations and experiments to analyze the rock fracturing mechanism and determine the optimal arrangement of fracturing holes when using hydro-mechanical splitters in tunnel excavation. First, a numerical model of rock fracturing is established using the cohesive-zone model, enabling analysis of the relationship between fracturing force and crack surface development during rock fracturing; this analysis involves examining the mechanisms for crack propagation and stress evolution, thereby comprehensively assessing the mechanism for rock fracturing using a hydro-mechanical splitter. Next, the stress evolution and crack propagation with multiple fracturing holes arranged in either a line or a circle are analyzed; how the fracturing force varies with different numbers of fracturing holes is obtained, and a method of using free-face unloading for circular expansion with a central free face is proposed. Finally, the tunnel contour control of rock fracturing using hydro-mechanical splitters is studied experimentally and ideal peripheral and bottom contours are obtained, thereby providing a way to use rock fracturing technology based on hydro-mechanical splitters for tunneling in hard rock.