Simulating the bluntness of TBM Disc Cutters in Rocks using Displacement Discontinuity Method

Underground accessibility includes several steps which the cutting step is the one of most basic and most important of them. Indentation of TBM disc cutters into the rock and producing of the chips in different scales are well known as an indentation process. This phenomena passe from producing the micro cracks to the coalescing into macro cracks. The present research focuses on the linear elastic fracture mechanics of rock and maximum shear stress criterion to investigate the micro crack propagation and its direction under disc cutters. A higher order indirect boundary element method (using quadratic displacement discontinuity elements) is used to estimate the stress intensity factors in rocks under single disc cutter. Also to eliminate errors caused by stress and displacement singularity near the crack tip, three special crack tip elements are used. As the TBM disc cutters will be eroded after a period of working, the effects of eroded and not eroded discs are numerically modeled, analyzed and compared with each other. To create the eroded disc model, we considered 4 small elements to generate the curvature of the cutter tip, which reducing the computing efficiency and increasing the required specific energy for chips formation.

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