ABSTRACT
In the work of Konietzky et al. (2009), simulation of subcritical crack growth and lifetime prediction of a rock specimen was realized by a noval application of the 2D Finite Difference Code FLAC (Itasca Consulting Group 2005). It is assumed the numerical model contains initial microcracks of different lengths according to certain probability distribution. Some simplifications have been made in their simulations making further improvement necessary. For example, the orientation of the microcracks was not considered, and maximum shear stress and minor principal stress were utilized in the subcritical crack
1 INTRODUCTION
The long term stability of geotechnical structures such as tunnels, mining shafts etc. has long been an important issue for safety considerations. As rock is the main load-bearing material in such structures, the lifetime (time to failure) of rock under load is of great practical interest for engineers and researchers. Time dependent behavior of rock has been studied by many researchers (Kemeny 1991, 2003, 2005, Sun & Hu 1997, Eberhardt 1998, Shao et al. 1999, Malan 1999, 2002, Aubertin et al. 2000, Masuda 2001, Miura et al. 2003, Chen et al. 2004, Chandler 2004, Shin et al. 2005, Amitrano & Helmstetter 2006, Lei et al. 2006, Jeong et al. 2007, Li et al. 2008, Damjanac & Fairhurst 2010, Jiang et al. 2012, Lu et al. 2014). Konietzky et al. (2009) proposed a lifetime prediction approach for brittle rocks under constant load. Numerical calculations were performed to simulate the time-dependent propagation and coalescence of microcracks, which finally lead to the failure of the rock. As a further development of this research work, this study improved the existing approach by introducing new crack propagation mode and stress intensity factor calculation scheme. The proposed scheme is studied through numerical simulations.
