Tunnel boring machine jamming anticipation based on a new monitoring system for real-time perception of shield strain

Tunnel boring machine (TBM) jamming has become one of the critical factors restricting the tunnelling speed and construction period of squeezing tunnels. To minimize the potential risk and damage of jamming accidents, a series of methods have been proposed to perceive TBM jamming under the condition of soft and fractured surrounding rocks. However, most of these methods cannot predict TBM jamming accurately in advance or perceive the jamming process in real-time. In the present study, a real-time monitoring system (composed of strain gauges, data acquisition, data transmission and data storage) for shield strain was developed and implemented in a TBM at the Lanzhou Water Resource Project in China. The shield strain of the double-shielded TBM was monitored and analysed continuously. The working conditions of the TBM (such as excavation or standstill, jamming or disjamming) were identified by analysing the characteristics of shield strain. The perception information was compared to the excavation records. The results indicate that there is good consistency between them. Combined with monitoring information and field surveys, the interaction mechanisms between the shield and surrounding rock were analysed qualitatively. The jamming mechanisms of the two accidents were revealed according to the variation in stable shield strain. A criterion for anticipation TBM jamming was proposed based on the shield strain characteristics (such as trend, amplitude, and magnification). These studies provide references for real-time perception and accurate anticipation of TBM jamming in soft and fractured surrounding rock conditions.