| Summary: | The rock breaking force of the disc cutter is the core parameter for studying the efficiency and safety of TBM excavation in hard rock tunnels, the key to improve the accuracy of the calculation model is how to match the calculation model with the rock breaking mode. Through the analysis of the intersection of cracks under different rock breaking modes and the leading factors of rock slices in the process of rock breaking by disc cutter, and considers that the rock is mainly damaged by compression and tension when the rock is broken by synergetic method, and the rock is mainly damaged by compression and shear when the rock is broken by non synergetic method, based on this, a new calculation method of tool load is proposed. The three-dimensional discrete element model of linear rock breaking with single and double hobs is established, and the lateral crack growth length under different penetration is counted. Based on this, the theoretical rock breaking mode under the combination of cutter spacing and penetration is calculated. The correctness of the theory of rock breaking mode division is verified by analyzing the intersection of cracks in the rock under various working conditions and the distribution of horizontal stress. Based on the distribution characteristics of internal cracks in rock, a calculation method for the volume of broken rock slices under synergetic and non synergetic rock breaking modes is proposed, the exponential function is used to fit the relationship between the thickness ratio of rock slag crushing and the cutter spacing, and the synergetic coefficient is defined β, and the expression of specific energy consumption is derived in combination with the new formula of rock breaking force. The results show that the errors of vertical force and rolling force calculated by the new rock breaking force model compared with the measured values are 7.3% and 11.0% respectively, which are smaller than those of CSM and linear calculation model. The rock breaking area depends on the rock breaking mode, the breaking area is mainly between the cutters in the cooperative mode, and in the non cooperative mode, it is below and on both sides of the cutter; As the cutter spacing increases, the high stress area in the rock gradually separates and moves upward, and the area decreases, and the optimal penetration increases, and the minimum specific energy consumption decreases. When the penetration degree increases, the specific energy consumption first decreases and then increases. Meanwhile, the change trend of the specific energy consumption curve is consistent with the relevant rock breaking test results.
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