Since early 1980's, research have been conducted on the prediction of tunnel boring machines (TBM) performance at the Earth Mechanics Institute (EMI) of Colorado School of Mines (CSM). The model for predicting the TBM performance are developed and named as the CSM model. The CSM model approaches are based on the TBM specification (i.e., thrust, torque and power) and rock properties including the uniaxial compressive strength, Brazilian tensile strength, and the brittleness of intact rock together with orientation and frequency of discontinuities in rock mass encountered. As the theoretical part of the model is improved in the institute, the utilized empirical database, updated continuously, is obtained from tunneling projects completed at the Earth Mechanics Institute of CSM since last couple of decades. In this study, the CSM model approaches for estimating the TBM performance in massive and fractured hard rock conditions are enlightened and discussed based on updated database.
Mechanical tunneling is a complex process and so it is difficult to account for all rock properties and features in a simple formula to estimate the machine performance. Several efforts have been performed to develop performance prediction models and theories offering explanations into the force-penetration behavior of rocks in the literature (Paul & Sikarski, 1965, Roxborough 1975, Ozdemir, 1977, Cook et al. 1984, Sanio 1985, Snowdon et al. 1983, Peng et al. 1989, Rostami & Ozdemir, 1993a,b, Rostami, 1997, Yagiz & Ozdemir, 2001, Yagiz, 2002, 2006, 2008). The analytical solution for indentation of mechanical tools into the rock begins with an analysis of stress in an elastic media under the point load. Paul & Sikarski (1965) proposed a theoretical model for wedge penetration, omitting the crushed zone occurrence phase and emphasizing the brittle chip occurrence phase for brittle isotropic rock.
