Abstract
In this work, a numerical model of rock breaking under hole assistance was established based on the finite element method (FEM) coupling with smoothed particle hydrodynamics (SPH) to reveal rock-breaking mechanisms and analyze the reasons for crack formation and propagation under hole assistance. In addition, the numerical model was verified by experiment with and without a hole, and the simulation results are basically consistent with the experimental results in rock breaking. During the process of rock fracturing, the hydraulic splitter was first inserted into the predrilling hole, and then the wedges were pushed into the rock under the action of the hydraulic pressure. In this process, the splitter wedge was separated from the two sides, and the transverse bursting force was transmitted to the rock. Finally, the main fracture formed and the rock mass broke due to the bursting force. The results show that the cracks propagate along the approximately straight lines OO1 (the distance between the auxiliary holes and the left predrilled fracturing hole) and OO2 (the distance between the auxiliary holes and the right predrilled fracturing hole) before extending to the auxiliary hole which is unlike the crack propagation in rock without auxiliary holes, and the crack propagating direction gradually approaches horizontally and is vertical to the side after passing through the auxiliary holes. Moreover, when the auxiliary holes are located at the prefabricated angles α = 40° and 45°, the crack propagation can be well induced and the cracks pass through the auxiliary holes. However, at α = 50°, the auxiliary holes can no longer well induce the crack propagation in the process of rock breaking; however, the fracturing pressure is still less than that with no auxiliary holes, indicating that the auxiliary holes play a positive role in guiding rock breaking.
Highlights
In China, the annual amount of rock roadway excavation is much greater than 2000 km, and the production of roadways accounts for 15% to 25% of total projects [1]
A numerical model of rock breaking under hole assistance is established based on FEM coupling with SPH to reveal the rock-breaking mechanism and explain the reasons for crack formation and propagation under hole assistance
According to the numerical simulation and experimental results in the scope of this research, the following conclusions were made: (1) e simulation crack propagation angles without auxiliary holes were approximately 30°, appearing on the lower left and upper right parts, and the simulation results are basically consistent with the experimental results
Summary
In China, the annual amount of rock roadway excavation is much greater than 2000 km, and the production of roadways accounts for 15% to 25% of total projects [1]. Us, a new method of rock breaking using a hydraulic splitter is proposed to solve this problem It has the advantages of safety, high efficiency, low cost, and so on (Figure 1). During the whole process of rock breaking, the relationship between the wedge depth and hydraulic pressure was not corresponding to each other, but a sudden step breaking occurred at a certain critical value under the action of complex tensile or shear stresses. At this time, the natural microcracks were partly
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