RAM Analysis of Hydraulic System of Earth Pressure Balance Tunnel Boring Machine

Earth Pressure Balance (EPB) Tunnel Boring Machines (TBMs) are more popular in urban mechanized tunneling nowadays. For improving the performance of these machines, time planning, maintenance scheduling and cost control in mechanized tunneling, tunnel boring machines should be reliable and maintained effectively and efficiently. For this aim, this paper seeks to study the reliability, availability and maintainability of hydraulic system of EBP-TBM in Tabriz metro in Iran. The failure and repair data were collected during about 26 months of machine operation. Performing trend and serial correlation tests showed that the data are Independent and Identically Distributed (IID) and therefore the statistical techniques were used for modeling. The data analysis showed that the Time Between Failures (TBFs) and Time To Repairs (TTRs) data confirm the generalized Gamma and Gamma distribution respectively. Reliability model indicated that reliability-based preventive maintenance time intervals for 90%, 80%, 70% and 50% reliability level are respectively 2.72, 7.17, 13.1 and 30.16 h. Calculations showed that TTR of this system varies in range 0.17- 6.5 h with 1.54 h as mean time to repair (MTTR).There is an 80% chance that the hydraulic system of EPB-TBM in Tabriz metro tunnel will be repaired within 2.45 h. Also the availability of hydraulic system of this machine is equal to 97%. The result provides a practical foundation and support for the RAM analysis of tunnel boring machines in mechanized tunneling.