Physical and numerical studies of rock fragmentation subject to wedge cutter indentation in the mixed ground

•The simulation and lab tests results are generally comparable under single cutter.•Asymmetric cutter forces and failure pattern induced in mixed ground indentation.•The penetration rate should be slowed down in mixed ground to prevent cutter damage. To study the effects of the mixed ground conditio...

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Published inTunnelling and underground space technology Vol. 71; pp. 354 - 365
Main Authors Zhang, Xiao-Ping, Ji, Pei-Qi, Liu, Quan-sheng, Liu, Qi, Zhang, Qi, Peng, Zhi-Hao
Format Journal Article
LanguageEnglish
Published Oxford Elsevier Ltd 01.01.2018
Elsevier BV
Subjects
Boring machines
BPM
Computer simulation
Cutters
Excavation
Force distribution
Inclination
Indentation
Machine tools
Mathematical models
Mixed ground
Rock fragmentation
Simulation
Skewed distributions
Stress concentration
Stress distribution
TBM
Tunnels
Wedge cutter
Wedges
Wedge cutter
TBM
BPM
Rock fragmentation
Mixed ground
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Summary:•The simulation and lab tests results are generally comparable under single cutter.•Asymmetric cutter forces and failure pattern induced in mixed ground indentation.•The penetration rate should be slowed down in mixed ground to prevent cutter damage. To study the effects of the mixed ground conditions on the cutter force and failure pattern during the tunnel boring machine (TBM) excavation, rock cutting tests under wedge cutter are conducted both in the physical experiments and the bonded particle model (BPM) numerical simulations. The results of simulation are generally comparable with those of experiments under single cutter. It demonstrates that the softer bottom material causes more disperse stress distribution which leads to wider AE accumulated area and more rapid displacement change in the indentation direction. Further simulations are conducted under double cutters. Crack may propagate deeper into the specimen due to the weaker bottom material. When the inclination of the material interface changes, the failure pattern of the specimen becomes highly asymmetric and the forces of the two cutters are not equal any more. Frequent change of ground conditions causes high asymmetric cutter force distribution, frequent changing cutter force as well as high eccentric moments on the cutter head.
ISSN:0886-7798
1878-4364
DOI:10.1016/j.tust.2017.09.003