Fragmentation characteristics of stressed rock with weak interlayers using double TBM cutters

• Published in: Engineering fracture mechanics Vol. 315; p. 110845
• Main Authors: Yang, Zheng, Tao, Ming, Yin, Tubing, Luo, Hao, Chen, Chao, Ranjith, P.G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 21.02.2025
• Subjects: Cutter spacing; Discrete element method; Initial stress; Rock breaking; Tunnel boring machine; Weak interlayer; Rock breaking; Initial stress; Tunnel boring machine; Discrete element method; Cutter spacing; Weak interlayer
• ISSN: 0013-7944
• DOI: 10.1016/j.engfracmech.2025.110845

•A model for stressed hard rock breakage containing weak interlayers is proposed.•The increase in initial stress inhibits the expansion of the median crack.•The presence of the weak interlayer leads to an asymmetry in the stress field.•The prediction equation for rock-breaking efficiency is established. Geological complexities, such as the presence of weak interlayers and elevated initial stress, are frequently encountered during tunnel boring machine (TBM) operations, leading to significant technical challenges and operational difficulties. To investigate the impact of weak interlayers and initial stress on rock breaking by double cutter, a discrete element model for stressed hard rock breakage containing weak interlayers considering actual penetration velocity was proposed for the first time. The crack extension, energy evolution, broken area, and cutter force during rock breakage were tracked by coding. The rock-breaking process and efficiency under different combinations of weak interlayers, initial stress, and cutter spacing were analyzed in detail. The results indicate that the peak difference in the force-penetration curves between the left and right cutters increases as the angle of the weak interlayer decreases. The asymmetry of the stress field generated by the double cutter indentation into the rock gradually increases as the weak interlayer is deflected from 90° to 30°. More attention should be paid to cutter wear when excavating tunnels containing weak interlayers with small angles (close to the direction of the free horizontal plane). Simultaneously, the increase in initial stress inhibits the expansion of the main intermediate crack, which is detrimental to rock breaking. Overall, the rock-breaking efficiency decreases with increasing initial stress. There is no simple positive or negative correlation between cutter spacing and rock-breaking efficiency. Eventually, the quantitative relationship between rock-breaking efficiency, initial stress, cutter spacing, and weak interlayer angle was established, which provides a feasible reference for designing the optimal rock-breaking method for similar projects in the future.