Evaluating the impacts of crew experience and selected activities on utilization of hard rock tunnel boring machines (TBMs)

Abstract

Estimating utilization rate is a critical factor for predicting performance of tunnel boring machines (TBM). The process of estimating machine performance, including rate of penetration and machine utilization must incorporate an understanding of site geology, TBM specifications and site set-up. The current study presents a preliminary analysis of the different activity time and downtime components from shielded TBMs tunneling through rock formations at two project sites to evaluate their impact on machine utilization. This study focuses on how selected tunnel activities, geological conditions and crew experience can impact the utilization of a TBM. The study has also involved implementation of these factors into a discrete event simulation (DES) model to estimate machine utilization. Time study measurements and other observational data were collected on-site at two tunnel projects. Time study data collected was synthesized into activity time distributions that were used as input parameters into a discrete event simulation model. In addition, the actual utilization of each project was calculated from the recorded data. A comparativeanalysis of the major processes associated with each TBM system is included in the thesis. The results of this analysis includes a list of uncertainties and associated risks for a typical rock TBM project involving shielded machines. The impact of the site geological conditions on overall utilization and specific tunneling activities was investigated. Furthermore, based on interviews with tunneling crews, effects of worker experience and time since last training on utilization during the learning phase of a project was explored. The main focus of this thesis is threefold. First, the activity time data collected during field studies was integrated into a database currently being developed at the Colorado School of Mines. The activity time distributions helped to refine the accuracy of the discrete event simulation model and then the actual utilization from both projects was estimated to analyze the validity of simulation model results. Second, this thesis provides a functional description and analysis of tunnel boring operation activities at two project sites using single shield TBMs. This work can be used to better understand the complex system at a modern tunneling project and provide a basis for determining site setup and logisticsat future project sites. Finally, this thesis highlights the advantages of collecting targeted TBM field data, including time studies for improving the operational efficiency and ultimately increasing the production and advance rates in tunneling projects. The analysis presented in this study will improve the accuracy of TBM performance prediction models and the viability of the discrete event simulation approach as a reliable method for prediction of machine performance as well as a tool for optimization of the tunneling process using TBMs for future tunneling projects.