Study of various models for the estimation of utilization of hard rock TBMs

Estimation of the Utilization factor (U) of the Tunnel Boring Machines (TBM) is one of the most important factors for the evaluation of time and cost of TBM tunneling. Utilization factor represents the efficiency of the operation of a TBM during the excavation of different sections of a tunnel and is defined as the proportion of TBM boring time over the total time. This factor is a function of many parameters such as geological conditions, machine specifications, and working conditions. Review of the literature shows that the advance rate and the utilization are much less studied than the penetration rate. The TBM utilization can be estimated either from the knowledge of different time components or directly from the geological parameters. This paper reviews different methods for the prediction of the utilization and the main problems involved in the process of such prediction. The results of a comparison between the predicted machine utilization rates and field performance indicate that the available models mostly overestimate the performance. A new model for the prediction of the utilization is developed based on the analysis of a database of more than 300 TBM projects’ records. The use of this database resulted in more accurate predictions.