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Abstract On the basis of reasonably simplifying the practical tunnelling conditions，the mechanism is mainly studied with simulation and experiment. First，in view of the effects of initial stress distribution of the cutters on crack propagation，Hertz elastic contact theory is introduced into the simulation. A model indenting into sandstone by TBM double-edged spherical tooth hob is established by using 2D discrete finite element simulation software UDEC. Based on the original linear cutting test-bed，an observational experiment is designed，in which the phenomena of rock crushing and bursting are captured by the high speed camera；and the producing process of compacting rock core is discontinuously recorded by the general digital camera skillfully. Crack production and propagation are successfully simulated. Results show that along with the increasing penetration，the compacting rock core is formed in the bottom of teeth for large compress stress. Side cracks between the teeth gradually propagate and tend to merge because of the tensile stress. The rock fragmentation is formed when the cracks are completely intersected. The phenomenon of bursting crack of small rock mass is caused by the tensile failure. The simulation results，which are suitable for studying the rock breaking mechanism of TBM in shallow-buried strata，have a good consistency with the experimental results and in-situ data.
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Received: 15 May 2009
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