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.
One of the most important parameters for predicting the TBM penetration rate is engineering properties of the rock mass. To predict TBM performance, several models have been developed by various researchers [1–14].The two main group of models include empirical and semi-theoretical approaches. The interrelationship between cutter wear, machine operation, continuous mucking, and support installations requires an evaluation of many factors affecting TBM performance. All mechanical rock-cutting tools share the same principles; hence, many efforts have been made to develop performance prediction models and theories offering explanations into the forcepenetration behavior of rocks [9, 14–20]. The rock cutting process deals with the indentation of a rock surface by a cutting tool. In the case of disc cutters, which are the most common cutting tool on hard rock TBMs, the indentation is followed by a forward movement, leaving behind it a groove and fractured and crushed rock [21]. The uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) of the rock are the most common rock properties in various mining and civil construction projects. These tests are often used as input parameters in TBM performance prediction models. However, the rock strength alone is not enough to predict penetration rate of the TBM, where the fractured faulted rock masses are to be encountered. Therefore, various rock tests and data evaluation techniques have been introduced to account for rock mass properties [9, 13, 21–24]. The most common models to predicting TBM penetration rate are the Colorado School of Mines (CSM) and the Norwegian University of Science and Technology (NTNU) performance models [1, 3].
