砂卵石地层高水压条件下盾构掘进喷涌控制研究

以兰州地铁1号线一期工程世纪大道站—中间风井区段为背景,综合运用现场调查与过程监测、实验室模拟试验、三维数值模拟等方法与手段,对砂卵石地层高水压条件下土压平衡盾构掘进基于渣土改良的喷涌控制的可靠性进行了研究。主要取得以下成果:(1)建立了砂卵石地层高水压条件下盾构掘进改良渣土抗渗性(喷涌控制)的定量试验模拟与测试方法;(2)确定了单掺钠基膨润土浆液改良渣土的膨润土浆液最优浓度和掺加膨润土浆液的最优体积比,并证明了其改良后的渣土的抗渗性能具有较高的喷涌控制可靠性;(3)同时掺加钠基膨润土浆液和泡沫改良渣土,泡沫的掺入体积比应小于1∶5。研究结果有力地支撑了世纪大道站—中间风井区段高水压条件下,盾构以-28‰的超大纵坡下坡掘进过程的喷涌控制,规避了盾构设备受淹风险。

Blowout control during EPB shield tunnelling in sandy pebble stratum with high groundwater pressure

Based on the earth pressure balance shield tunnelling of Shijidadao station to the ventilation shaft section of Lanzhou metro line 1, the blowout control of conditioned muck in sandy pebble stratum with high groundwater pressure is studied through field investigation, laboratory tests and three-dimensional numerical modelling. It is mainly concluded that: (1) A method is established for testing the anti-blowout of conditioned muck in laboratory; (2) The optimum concentration of sodium-based bentonite slurry and the optimum volume ratio of slurry to soil of the conditioned muck are determined, and the reliability of the anti-blowout of the conditioned muck is verified; (3) The volume ratio of foam to soil of the conditioned muck should be less than 1∶5 when using slurry and foam. The results of this study may guide shield tunneling at the section with the maximum longitudinal grade of -28‰ so as to effectively avoid shield-flooding risks due to blowout.