西三线长江盾构断层带分析与风险应对措施

Fault zones along the Yangtze River crossing and countermeasures against risks in shield-driven tunneling for the 3rd West-to-East Gas Pipeline

受地质因素影响,盾构施工过程中存在一定风险。西三线中段长江盾构穿越断层56处,最宽断层为14 m,其他断层宽度为1~10 m不等,断层带中多分布宽度小于30 cm的石英结晶体。断层带部位因地质软硬不均、含水量大,容易出现地层超挖导致地面沉降风险;石英脉结晶体具有体积小、强度高的特性,与周围的围岩强度差距大,不易被钻孔发现,施工中容易产生刀盘卡阻、刀具严重磨损、周边围岩不稳等风险。针对长江盾构地质复杂的特点,结合以往工程施工经验及对盾构设备的研究,提出了针对性的施工措施,并首次提出了盾构机、刀盘和刀具整体选型要求,可为国内岩石地层盾构机选型及施工提供参考。

Shield-driven tunneling may involve certain risks due to geologic conditions. The middle section of the 3rd West-to-East Gas Pipeline crossing the Yangtze River encounters 56 faults in shield-driven tunneling. The maximum width of fault is 14 m, and most of these faults have widths at 1-10 m. These faults mostly contain veins of quartz crystals with distribution widths not more than 30 cm. With uneven distribution of geologic conditions and significant water contents, these fault zones may suffer ground subsidence because of overbreak. Since crystals in quartz veins are characterized by lower volumes, high strength and significant contrast in strengths with surround matrix, it is not easy to identify quartz veins during drilling. Consequently, drilling operations in these formations may encounter disc jamming, severe abrasion and instability of matrix. With consideration to complex geologic features encountered in shield-driven tunneling for the Yangtze River crossing and previous experiences in shield-driven tunneling, together with understanding to relevant facilities, specific countermeasures are proposed. In addition, specific requirements for the shield machinary, discs and cutting devices are raised for the first time. Relevant research results may provide valuable references for operations and selection of shield machinary in rock formations in China.