A tunnel boring machine (TBM) is the primary resource in a tunnel construction project and generally its advance rate is equal to the performance rate of the whole project. Regarding previous studies, the utilization factor of TBMs is approximately 50% most of the time. The process of repair and maintenance of various parts of the machine and the logistic equipment takes 50% of the time.
This case study aims to simulate all processes of TBM tunneling in Ahwas subway project, using discrete-event simulation method, and find out how different scenarios of repair and maintenance can affect the utilization factor of the TBM. The simulated processes in the cycle of TBM tunneling include:
- logistic supports of the TBM using locomotives and rolling stocks and their movement inside the tunnel,
- loading tunnel segments and unloading muck from rolling stocks in the tunnel portal,
- excavation of tunnel by the TBM,
- mounting segments to support the tunnel against earth collapse,
- impairment of different parts of the machine and the process of repair and maintenance of the TBM.
The results of the model show that changing the policy of repair and maintenance of the TBMs in the project can improve the utilization factor of them. This model can be implemented in other tunneling projects to test different policies of TBMs’ repair and maintenance.