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)〖HJ6.5mm〗 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 need to make great efforts to achieve 90% of the equipment system′s availability and over 40% of the tunneling efficiency.

北疆供水二期工程总长540 km，主要由西二隧洞（139.04 km）、喀双隧洞（283.27 km）和双三隧洞（92.15 km）组成，隧洞占总长度的95.6%，均为深埋超特长隧洞，其中喀双隧洞是目前世界上已建和在建的最长输水隧洞。分析本工程的特点及地质情况，得出主要施工难题为长距离掘进关键设备耐久性、穿越断层破碎带、围岩突涌水防控、长距离独头通风及运输、反坡排水、破岩效率及快速掘进等。试掘进结果表明： 1）勘察设计提供的地质情况与施工揭示的地质情况基本一致，这为高效掘进提供了基本条件。2）敞开式TBM能较好地适应Ⅱ、Ⅲ类围岩、节理裂隙带及小规模断层；而对于规模较大的断层破碎带及富水地层，则适应性较差，还有待于从设备、支护及施工技术方面加以改进。3）试掘进阶段TBM设备系统平均完好率达89.9%，但仍有一些设备故障率较高，有的还出现了主轴承密封圈漏油现象；为了实现长距离掘进，还需进一步提高设备的可靠性和耐久性。4）试掘进阶段平均纯掘进时间占比为29.6%，其中双三Ⅱ标TBM1平均纯掘进时间占比高达45.2%，最高月进尺达到1 280 m，创造了国内同类地质条件掘进最高记录。5）随着掘进进尺的不断增加，TBM集群要达到设备系统90%以上的完好率、支撑40%以上的纯掘进工时率的目标，还需要付出巨大努力。