Kerfing on the tunnel working face is one of effective ways to promote the performance of tunnel boring machines (TBMs) in hard rock masses, since the rock mass integrity is reduced. When TBM cutter cuts along the midline of two kerfs, the lateral cracks generated from the cutter tip could propagate to the bottom of adjacent kerfs, thus improving the cutting efficiency. However, the cutter vibration under such circumstance was rarely investigated. To analyze the impacts of kerf depth and cutter penetration on the cutter vibration, a series of full-scale linear cutting tests were conducted on two granite samples with high strength. Kerfs of different depths were processed by the saw before each cutting on one sample, while conventional cuttings without kerfs were performed on the other one to make a comparison. A vibration monitoring system was installed in the cutter holder, three axial accelerations and forces of the cutter were recorded during the tests. Rock mucks were collected and sieved to obtain the muck mass and coarseness index. It was found the intense cutter vibration induced by the intact rock cutting could be alleviated by kerfs. The most severe vibration was found in the cutter normal direction thus needed to be focused on. A greater cutter penetration depth made the vibration more intense. The kerf depth had quadratic correlations with various vibration parameters, indicating there was a critical depth beyond the which the vibration could be greatly alleviated, while the higher rock breaking efficiency could be also guaranteed. The critical depth obtained was about 6–9 mm within the range of experimental design. Variational mode decomposition (VMD) was introduced to extract two main subbands and their central frequencies in the frequency domain. The central frequency of the lower frequency band had a bell-shaped correlation with the kerf depth, the critical depth was still found at 6 mm. The findings are conducive to the design of the kerf-assisted TBM tunnelling and the prolongation of cutter life.

中文翻译：

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不同深度切缝辅助TBM滚刀破岩振动分析

隧道工作面开缝会降低岩体完整性，是提高硬岩隧道掘进机 (TBM) 性能的有效方法之一。TBM刀具沿两个切缝中线切割时，刀尖产生的横向裂纹可扩展至相邻切缝的底部，从而提高切割效率。然而，这种情况下刀具振动的研究却很少。为了分析切缝深度和刀具穿透力对刀具振动的影响，对两个高强度花岗岩样品进行了一系列全尺寸线性切削试验。其中一个样品在每次切割前用锯子加工出不同深度的切缝，而另一样品则进行常规无切缝切割进行比较。刀架上安装了振动监测系统，测试过程中记录了刀具的三个轴向加速度和力。收集岩渣并过筛，得到岩渣质量和粗度指数。研究发现，完整岩石切削引起的强烈刀具振动可以通过切缝来缓解。最严重的振动出现在刀具法线方向，因此需要重点关注。刀具穿透深度越大，振动越剧烈。切缝深度与各种振动参数呈二次相关，表明存在一个临界深度，超过该深度可以大大减轻振动，同时也能保证较高的破岩效率。获得的临界深度在实验设计范围内约为6-9 mm。引入变分模态分解（VMD）来提取频域中的两个主要子带及其中心频率。较低频段的中心频率与切缝深度呈钟形相关，临界深度仍为6 mm。研究结果有助于切缝辅助TBM隧道设计和延长刀具寿命。