Cutter change time and cutter consumption for rock TBMs

Abstract

This paper discusses common methodologies used in the prediction of cutter change time (the average time required for changing a cutter on the cutter head) and cutter consumption (the average number of cutters worn out for the excavation of 1000 cubic meter of rock) and highlights some potential pitfalls in the process. For this purpose, the prediction capabilities of these methods are discussed and their validity is examined using detailed data from many tunnels from around the world. The results of the statistical analyses and comparative studies show that in most cases, the NTNU model underestimates cutter change time. The average cutter change time is approximately 66 min for different cutter sizes and there is a minimal difference between corresponding values of the large versus small cutters. A new cutter change time model is also developed using a statistical analysis of a database of 50 TBM projects’ records based on the TBM penetration rate and quartz content of the rock. Analysis of the cutter consumption information of several tunnel projects has revealed that the available models for the estimation of this parameter require some revisions in the structure of their formulas. A new cutter consumption model is also developed based on a statistical analysis of a database of 135 TBM projects’ records. The results show the proposed new model’s estimates are in good agreement with the actual values with a high coefficient of determination (78%). The outcomes of this paper can improve rock TBMs’ performance and project planning evaluation especially for the early stage of a tunneling project.