stress is one of the important geological factors affecting Tunnel Boring Machine (TBM) performance. Meanwhile, cutter wear is also a nonnegligible issue in TBM tunneling. In this work, a continuum-discontinuum approach, the finite-discrete element method (FDEM) is employed to explore the impact of confining stress on rock breaking and optimum cutter spacing. Firstly, the evolution of system kinetic energy and rock surface displacement during confining stress equilibrium is revealed. Then, a series of adjacent cutter-indentation tests are performed to analyze the rock fracture pattern and its transformation law, cutter force and the vertical extent of the fracture zone, which is compared with the existing experimental and numerical results. Finally, a fragment extraction algorithm is adopted to count fragment shape and area, and the specific energy () is quantitatively analyzed according to fragment area and cutter work. Besides, the cutter force and cutting performance with different existing wear are discussed. Results indicate that the maximum cutter force increases and the vertical crack propagation is more suppressed as confining stress increases. Overall, the rock fragment area increases first and then decreases with the increase of cutter spacing under all confining stresses, while the optimum cutter spacing increases as confining stress increases. Moreover, the rock breaking efficiency is the highest with a confining stress of 3 MPa and a cutter spacing of 114 mm. The existing wear increases the cutter work and reduces TBM performance. The findings are helpful in the design of TBM cutterhead in tunnel excavation under different stress conditions.

中文翻译：

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连续-不连续介质法研究围压下TBM滚刀的破岩及最佳间距


应力是影响隧道掘进机（TBM）性能的重要地质因素之一。同时，刀具磨损也是TBM隧道掘进中不可忽视的问题。在这项工作中，采用连续-不连续方法，有限离散元方法（FDEM）来探索围岩应力对岩石破碎和最佳刀具间距的影响。首先，揭示了围压平衡过程中系统动能和岩石表面位移的演变。然后，进行一系列相邻刀具压痕试验，分析岩石破裂模式及其转变规律、刀具受力和破裂区的垂直范围，并与现有的实验和数值结果进行比较。最后采用破片提取算法计算破片形状和面积，并根据破片面积和刀具做功定量分析比能（）。此外，还讨论了不同磨损情况下的切削力和切削性能。结果表明，随着围压的增加，最大切削力增加，垂直裂纹扩展受到更多抑制。总体而言，在所有围压下，随着刀齿间距的增加，碎岩面积先增大后减小，而最佳刀齿间距随着围压的增大而增大。围压为3 MPa、刀齿间距为114 mm时破岩效率最高。现有的磨损增加了刀具工作并降低了 TBM 性能。研究结果有助于不同应力条件下隧道开挖中TBM刀盘的设计。