Simulating the crack propagation and cracks coalescence underneath TBM disc cutters
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ORIGINAL PAPER
Simulating the crack propagation and cracks coalescence underneath TBM disc cutters Hadi Haeri 1 & Mohammad Fatehi Marji 2
Received: 17 February 2015 / Accepted: 18 September 2015 # Saudi Society for Geosciences 2016
Abstract A coupled numerical-experimental analysis of crack propagation, cracks coalescence produced during the cutting action of TBM disc cutters has been studied. A numerical code is developed based on the higher order semi-infinite displacement discontinuity method (HSDDM) for the numerical simulation of rock-cutting process. A quadratic displacement discontinuity variation along each boundary element is assumed to evaluate the mode I and mode II stress intensity factors (SIFs). Based on the linear elastic fracture mechanics (LEFM) theory, the maximum tangential stress criterion is implemented in the HSDDM2D code for predicting the crack initiation and its direction of propagation (cracks propagation path). Some experiments were done to evaluate the final breakage path during the cutting process of disc cutters in rock-like specimens. The same experimental specimens have been numerically modeled by a higher order semi-infinite indirect boundary element method. The numerical and experimental results are in good agreement and demonstrate the accuracy and effectiveness of the proposed numerical method. Rock-cutting mechanisms under single and double type discs are simulated by HSDDM2D. Effects of some specific disc parameters, i.e., penetration depth (Pd) and S/Pd ratio (ratio of disc spacing (S) to penetration depth (Pd)) on the specific energy (ES) are also investigated. Keywords Rock-cutting process . TBM disc cutters . HSDDM2D . Experiments * Hadi Haeri [email protected]; [email protected]
1
Department of Mining Engineering, Bafgh Branch, Islamic Azad University, Bafgh, Iran
2
Mine Exploitation Engineering Department, Faculty of Mining and Metallurgy, Institution of Engineering, Yazd University, Yazd, Iran
Introduction The widespread application of rock-fracturing methods with mechanical tools in mining and civil engineering operations indicates the significance of rock fracture mechanics principles which can be used with prediction and estimation procedures in optimization of planning, time, and economic schematization of projects. Rock excavation tools (such as drilling bits and tunnel-boring machines (TBM) disc cutters) have been widely used in drilling operation and in the construction of modern tunneling and underground spaces (Howarth and Roxborugh 1982; Cook et al. 1984; Guo et al. 1992; Acarglu et al. 2008; Cho et al. 2010; Bilgin et al. 2012). Due to brittleness and elastic behavior of most rock materials, the indentation process of rock-cutting tools (drilling bits and disc cutters) involve the initiation, propagation, and coalescence of the induced micro-cracks and cracks in the rock medium underneath the cutting tools during their excavating operations (Tarkoy 1973; Farmer and Glossop 1980; Bilgin et al. 2000; Bael and Moon 2003; Benardos and Kaliampakos 2004;
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