The rock breaking mechanism plays a significant role in TBM (tunnel boring machine) performance prediction, which has not yet been understood satisfactorily. In this work, a series of rotary cutting simulations via a particle-based DEM (discrete element method) for mudstone were conducted to explore the rock breaking mechanism and cutter-rock interaction during TBM tunnelling. Different cutting scenarios were considered. The rock breaking events were inferred from the breakage of bonds between particles constituting the mudstone. The spatial distribution of microcracks was obtained in the form of bond breaks between particles. The cracking features of mudstone are different from those reported for hard rocks. The characteristics of the contact stress distribution were also analysed and fitted by a combined Hertz-Weibull model. The distribution ranges of bond breaks and cutter-rock contact stress are both positively related to the penetration depth but not largely dependent on the cutting radius. However, the side force has a negative relationship with the cutting radius, and this dependency is more significant with increasing penetration depth. The bond-break distribution is skewed to the outer side of the cutter due to different cutting trajectories and centrifugal effects. Moreover, the bonds tend to break towards the existing cutting groove due to the release of radial confinement. The variation in cutting forces interrelates with the bond breakage events, which reduces the local stiffness and strength of the rock. The existence of the former cutting groove yields eases rock breakage and associated smaller cutting forces.

Graphical abstract

中文翻译：

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泥岩 TBM 掘进过程中刀岩相互作用机制研究：来自旋转切削试验 DEM 模拟的见解

破岩机理在 TBM（隧道掘进机）性能预测中发挥着重要作用，目前尚未得到令人满意的认识。在这项工作中，通过基于粒子的 DEM（离散元法）对泥岩进行了一系列旋转切割模拟，以探索 TBM 掘进过程中的岩石破碎机制和刀具-岩石相互作用。考虑了不同的切割方案。从构成泥岩的颗粒之间的键断裂推断出岩石破裂事件。微裂纹的空间分布以颗粒之间的键断裂的形式获得。泥岩的开裂特征与报道的硬岩不同。接触应力分布的特征也通过组合的 Hertz-Weibull 模型进行了分析和拟合。断键和刀石接触应力的分布范围均与切入深度正相关，但与切削半径的关系不大。然而，侧向力与切削半径呈负相关，并且这种依赖性随着穿透深度的增加而更加显着。由于不同的切割轨迹和离心效应，断键分布偏向刀具外侧。此外，由于径向约束的释放，结合倾向于向现有的切割槽断裂。切削力的变化与键断裂事件相关，从而降低了岩石的局部刚度和强度。前切削槽产量的存在减轻了岩石破碎和相关的较小切削力。

图形概要