With widespread applications of mechanized tunneling in almost all ground conditions, prediction of anticipated performance and production rate of tunnel boring machine (TBM) is essential part of planning, cost estimation, and selection of proper machine specification to achieve efficient and safe operation. Penetration rate is a principal measure of TBM performance and is used to evaluate the feasibility of using the mechanized tunneling. This paper will review machine performance of a hard rock TBM in 12.24 km long tunnel between Maroshi and Ruparel College which is being constructed to improve the water supply system of Greater Mumbai, India. Analysis of field performance data has been used to evaluate the relationship between various lithological units and TBM operation. The results of statistical analysis of the initial 5.83 km long tunnel between Maroshi and Vakola indicate a strong relationships between geomechanical parameters and TBM performance parameters in this particular project. A site specific empirical model is introduced to estimate TBM performance in this project, which could show the trends and anticipated variations in machine performance as a function of ground conditions and common rock mass properties in similar conditions.
Hard rock tunnel boring has become more or less the standard method of tunneling for tunnels of various sizes with lengths over 1.5–2 km. Estimating the performance of TBM is a vital part of tunnel design and selection of the most appropriate excavation machine. During the past three decades, numerous TBM performance prediction models for evaluation of TBM have been proposed. In brief, all the TBM performance prediction models can be divided into two distinguished approaches, namely theoretical and empirical ones (Rostami et al. 1996). Currently, two models including Colorado School of Mines or CSM (Rostami 1997) and Norwegian University of Science and Technology or NTNU (Blindheim 1979, Bruland 1998) models are the most recognized TBM performance prediction and prognosis models in use around the world.
The CSM model allows calculation of the cutting forces that need to be applied to a disc in order to reach a certain penetration into the rock. This method offers the advantages of being able to consider the geometry of the disc and cutterhead (the diameter of disc and the distance between the grooves) in detail. However, the original CSM model does not consider the natural discontinuities of the rock mass, which have an important influence on the net advancement speed on the TBM. Yagiz (2002) has offered some modifications to the original CSM model by adding rockmass properties as input parameters into the model. Also, Ramezanzadeh (2005) has followed up on this work and developed a database of TBM field performance for over 60 km of tunnels. He offered adjustment factors for CSM model to account for joints and discontinuities.
