The EPB TBM “CREC 1105”, developed and manufactured by China Railway Engineering Equipment Group Co., Ltd. (CREG), is successfully applied in the construction of Chongqing Rail Transit Line 15. The TBM mainly goes through sandstone and sandy mudstone with the grade IV surrounding rock and abundant water content in strata. The TBM also goes under a variety of municipal pipelines and passes through near the residential area, which puts forward higher requirements on TBM safety performance. In order to safeguard the project construction, CREG has developed a TBM tail sealing safety warning system to monitor such abnormal conditions as pressure loss, tail brush wear, etc.
In order to better monitor the tail grease pressure, CREG has specially researched and developed a tail grease pressure sensor with stronger environmental adaptability, whose pressure measurement range is 0-6MPa and measurement accuracy is 0.5%. On the basis of seal cavity dimensions, CREG has also designed the optimal sensor quantity, sensor spacing and other installation parameters to realize the accurate pressure measurement of whole seal ring with high-viscosity tail grease, which can compensate for the poor sensitivity of current seal performance estimation by grease injection pressure.
During the project construction, this system runs smoothly and the sensing devices works stably and reliably, which realizes the all-round and real-time perception of tail seal cavity. It not only realizes the monitoring of pressure loss of tail seal cavity but also reminds the control cabin operator to timely adjust the grease injection method and parameters according to the monitored parameters, which ensures the safe construction and saves the grease consumption that amounts to appropriately 100,000 Chinese yuan. With this system, the TBM has excavated 3.4km successfully and safely, and broken through the first section, during which the safe, reliable, green, environmental-friendly and efficient construction requirements have been reached and the safety and quality management levels have been improved.
According to the control cabin operator of this project, “this TBM tail sealing safety warning system currently plays the role of important reference data during tunnelling in high water pressure strata, which can directly guide the adjustment of tunnelling parameters and the determination of tail grease injection volume. In addition, it can ensure the safety, improve the efficiency and save the costs for TBM tunnelling.”