Recommended rock testing methods for predicting TBM performance: Focus on the csm and Ntnu models

The performance and efficiency of tunnel boring machines (TBM) depend on the rock properties and geological structures, and machine specifications and operational parameters. Several predictor models are currently available for estimation of TBM performance in rock masses. Models developed by the Colorado School of Mines (CSM) and the Norwegian University of Science and Technology (NTNU) are two most common predictors for estimating the TBM performance. Each model utilizes different input parameter for predicting the TBM penetration rate. Also they use different rock testing methods to obtain related rock properties. The CSM Model is based on force equilibrium method and uses intact rock properties including uniaxial compressive strength (UCS), Brazilian indirect tensile strength (BTS) and abrasiveness of rock. The NTNU Model is empirical method and focuses on geological structures such as joint, plane of weakness, bedding as well as porosity, brittleness, and abrasiveness of rock. Also, the Modified CSM Model that were developed based on comparison of the predictions of the base CSM Model and field data has been introduced by some researchers. The new model includes rock brittleness and the rock fracture properties as adjustment factors into the existing model. These approaches are briefly discussed in this paper. This paper will compares these models and their input parameters, their input variables as well as predicted performance results. Further relevant rock properties and related laboratory testing methods will be highlighted.