Theoretical analysis of JMC effect on stress wave transmission and reflection

Taking the joint matching coefficient(JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model(CIM-JMC) was established in this study to describe the wave propagation across a single joint. According to this model, the reflected and transmitted waves at the joint were obtained, and the energy coefficients of reflection and transmission were calculated. Compared with the modified Split Hopkinson pressure bar(SHPB) experiment, it was validated by taking the incident wave of the SHPB test as the input condition in the CIM-JMC, and the reflected and transmitted waves across the joint were calculated by the model. The effects of four sets of JMCs(0.81, 0.64, 0.49, and 0.36) on the transmission and reflection of the stress wave propagation across the joint were analyzed and compared with the experimental results. It demonstrated that the values of CIM-JMC could represent both the transmission and reflection of the stress wave accurately when JMC > 0.5, but could relatively accurately represent the reflection rather than the transmission when JMC < 0.5. By contrasting energy coefficients of joints with different JMCs, it was revealed that energy dissipated sharply along the decrease of JMC when JMC > 0.5.

极硬极高磨损岩石中的TBM 隧道施工:问题,解决方案和辅助破岩方法

极硬极高磨损岩石将增大TBM刀具磨损、降低掘进速率,给施工带来极大挑战。为了应对该类地层,设备制造商和研究人员通过提高TBM性能和开发辅助岩石破碎方法,进行了大量探索。本文首先通过案例分析,概述了极硬岩中TBM施工的诸项挑战;其次,综述了硬岩TBM的技术突破和各种可以用于独立/辅助破碎硬岩的方法;而后,详细阐述了高压水射流、激光和微波辅助破岩的机理、实验室研究、现场应用以及未来需要开展的研究方向。整体而言,这些辅助破岩方法在技术上是可行的,然而其独立破岩比能通常是机械破岩比能的10倍以上,因此需要研究辅助方法-机械联合破碎极硬岩的比能,另外需开发脉冲型水射流、激光和微波技术,使其应用更有经济性。