Disc-cutter induced rock breakage mechanism for TBM excavation in rock masses with different joint shear strengths

Abstract

When tunnel boring machines (TBMs) excavate through jointed rock masses, the cutting efficiency is strongly affected by the shear strength of joints, the mechanism of which, however, remains poorly understood. In this study, a series of disc-cutter indentation tests were conducted on granite rock mass specimens with different joint shear strengths. During the indentation, the cracking process was recorded by a digital image correlation (DIC) system. The deformation and strength of specimens, cracking behavior, rock breakage mode and cutting efficiency were quantitatively investigated. In addition, to investigate the combined effects of joint shear strength, orientation and spacing on the rock breakage mechanism, numerical rock mass models were established based on a particle flow code PFC2D. Experimental results reveal that the cracking of primary and secondary cracks changes from the mixed shear-tensile to tensile mode in the initial stage, while the joint shear strength does not affect the cracking mode in the subsequent propagation process. The rock breakage mode is classified to an internal block breakage mode, a cross-joint breakage mode and a cutters-dependent breakage mode. The cross-joint breakage mode is optimal for improving the cutting efficiency. Numerical simulation results reveal that the increase in the joint shear strength changes the internal block breakage mode to cross-joint breakage mode for rock masses of particular ranges of joint orientation and spacing. These findings provide basis for improving the TBM cutting efficiency through jointed rock masses.

Keywords

Indentation test / Joint shear strength / Disc cutter / Rock breakage mechanism / Cutting efficiency

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

Bolong Liu: Methodology, Software, Writing - original draft. Bo Li: Data curation, Investigation, Supervision, Writing - review & editing. Liang Zhang: Data curation, Formal analysis, Resources. Rui Huang: Methodology, Validation. Huicai Gao: Resources, Visualization. Shilin Luo: Data curation, Visualization. Tao Wang: Investigation, Validation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The financial support from the National Natural Science Foundation of China (Grant Nos. 41831290, 41907167 and 51708354), Natural Science Foundation of Zhejiang Province (Grant No. LTGS23E040001) and Natural Science Foundation of Hunan Province (Grant No. 2022JJ40521) is greatly appreciated.

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