城陵矶穿越长江水下软硬不均地层隧道修建技术

城陵矶穿越长江隧道全长2 756.379 m,根据地层不均匀的地质条件,为节省投资并确保水下施工的安全,在长江南岸以及长江主河道以下地质条件复杂、断层破碎带密集的地段采用盾构法施工,施工长度2 011.379 m;在长江北岸隧道穿越地质条件较好、埋深较大的河床段采用矿山法施工,施工长度745 m;竖井上部软弱地层采用沉井法施工、下部硬岩采用钻爆法施工。盾构法施工中,选择泥水加压复合式盾构机,并选择复合式刀盘。在低水压地段采用泥水平衡模式,在高水压地段采用加气模式掘进,并根据地质条件变化及时调整掘进参数。施工中通过同步注浆、二次注浆及堵水注浆等不同注浆方法充填衬砌背后空隙保证防水效果。矿山法施工中,采用红外探水和超前钻探等方法进行超前地质预报、全断面帷幕注浆及小导管注浆加固围岩、微震动爆破开挖减小对围岩的扰动等防突涌水施工技术。在施工全过程中,运用监测与信息反馈技术进行信息化施工,确保了优质、安全、快速施工。

Construction Technology of Chenglingji Yangtze River Crossing Tunnel in Hard-Soft Heterogeneous Ground

Chenglingji Yangtze River crossing tunnel is 2 756.379 m long.In order to minimize the investment and to ensure the construction safety under Yangtze River,shield-driven tunneling method is adopted for the 2 011.379 m long tunnel portion on the south bank and under the main watercourse of the Yangtze River,where there exist complex geological conditions and concentrated faults and fractured zones.While mined tunneling method is adopted for the tunnel portion on the north bank of Yangtze River where the geological conditions are better and the tunnel portion under the riverbed with deeper overburden,with a total length of 745 m.Due to the hard-soft heterogeneous geological conditions,composite pressurized slurry shield machine with composite cutterhead is adopted.In tunnel portions with low water pressure,slurry balanced mode is adopted.While air compressed mode is adopted for tunnel portions with high water pressure.The boring parameters are adjusted timely in accordance with the changes of the geological conditions.During the tunnel boring,various types of grouting,such as simultaneous grouting,secondary grouting and water-sealing grouting are conducted so as to backfill the space on the back of the lining and to achieve waterproofing effect.During the mined tunneling,such advance geology forecasting methods as infrared water detecting and advance borehole drilling are adopted.Such reinforcement measures as full-face curtain grouting and small-duct grouting are taken and micro-vibration blasting technology is adopted in the tunnel excavation to minimize the disturbance to the surrounding rock mass,so that water in-rushes and water inflows can be prevented.During the complete process of the tunnel construction,monitoring and measurement are conducted and monitoring results are fed back,so as to ensure high quality,high safety and high speed of the tunnel construction.