13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Simulating the bluntness of TBM Disc Cutters in Rocks using Displacement Discontinuity Method Hadi Haeri1, *, Kourosh Shahriar2, Mohammad Fatehi Marji3, Parviz Moarefvand4 1PhD candidate of rock mechanics, Mining Engineering Department, Science and Research Branch, Islamic Azad University, Poonak, Hesarak, Tehran, Iran 2Prof., Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran 3Associate Prof., Head of Mine exploitation Engineering Department, Faculty of Mining and Metallurgy, Institution of Engineering, Yazd University, Yazd, Iran 4Assistant Prof., Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran * Corresponding author: hadihaeri@ymail.com Abstract 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 passé 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. Keywords: eroded disc, micro crack propagation, specific energy, SDDM, TBM 1. Introduction One of the most complex engineering problems is cutting and indentation of mechanical tools into the rock which has been considered by human primitively. The investigation on rock fracture mechanics with mechanical tools in mining and civil operations is significant duo to its widespread applications. These investigations can be used to predict and estimate rock fracture mechanism for optimization and risk-reducing of planning, temporal and economic schematization [1]. The key parameters in TBM head design are head diameter, number of cutters, thrust force, rolling force, RPM, penetration depth, and cutter spacing [2, 3 and 4]. Many experimental studies and numerical simulations have been reported for the breakage mechanism of rock under disc cutters of tunnel boring machines (TBMs) [5-16]). Recently, Cho et al [4] investigated the optimum spacing of TBM
RkJQdWJsaXNoZXIy MjM0NDE=