Construction of a Long-distance and Shallow-buried Tunnel Using Curved Pipe Roof and Freezing Method: Gongbei Tunnel of Hong Kong-Zhuhai-Macao Bridge Project

ZHANG Jun ;WU Shuyuan ;CHENG Yong ;LIU Jiguo

Tunnel Construction,2019,Vol 39,No. 01

Analysis of Adaptability of TBM in Trial Boring Stage of Super-long Tunnel

DENG Mingjiang;TAN Zhongsheng

Tunnel Construction,2019,Vol 39,No. 01

The total length of the 2nd stage water transfer project in the northern area of Xinjiang of China is 540 km. The project consists of three tunnels, namely, Xi-Er (XE) Tunnel, Ka-Shuang (KS) Tunnel and Shuang-San (SS) Tunnel, with lengths of 139.04 km, 283.27 km and 92.15 km respectively. All of these three tunnels have deep cover and are super-long tunnels, and 95.6% of the total length of these three tunnels is constructed by TBMs. KS Tunnel is the longest water tunnel built or under construction in the world. In the paper, the trial TBM boring scheme and schedule of the water transfer project are introduced; the geological conditions revealed are statistically analyzed; and main project difficulties, i.e., durability of key equipment in long distance driving, passing through fault and fracture zones, water inrush, single-head ventilation and transportation in long-distance tunneling, anti-slope drainage, and rock breaking efficiency and boring efficiency, are put forward. The adaptability of the TBMs used is analyzed from the aspects of adaptability to different surrounding rocks, adaptability to bad geological conditions and countermeasures, long-distance ventilation and belt conveyor mucking and countermeasures, and TBM boring stability (such as equipment availability, boring time proportion, system malfunction and operation time). The following conclusions are obtained: (1) Accurate geological survey is the precondition of efficient tunneling. (2) The open type TBM can better adapt to Grade Ⅱ and Ⅲ of surrounding rocks, jointed and fractured zones and small faults; the adaptability of the TBMs used to the large-scale fault-fracture zones and water-rich strata in this project is poor, and it needs to be improved in aspects of TBM equipment, supporting and construction technology. (3) The average availability of the TBM equipment in the trial boring stage is 89.9%; however, the malfunction rate of some ancillary equipment is high, particularly oil leakages occur to the main bearing seals; in order to achieve long-distance tunneling, it is necessary to further improve the reliability and durability of the TBM equipment. (4) The average net boring efficiency in the trial boring stage is 29.6%, and TBM1 in Section Ⅱ of SS Tunnel achieves up to 45.2 % net boring efficiency; and highest monthly progress rate is 1 280 m, which created the highest record of the open type TBM boring in China. (5) TBM needs to make great efforts to achieve 90% of the equipment system’s availability and over 40% of the tunneling efficiency.