中粗砂-风化岩复合地层双模盾构渣土改良技术研究

Soil Conditioning Technology for Dual-Mode Shield Tunneling in Medium Coarse Sand-Weathered Rock Composite Strata

为解决中粗砂-风化岩复合地层土压-泥水双模盾构土压平衡模式施工适应性问题,依托广州地铁12号线赤沙滘站—仑头站区间隧道工程,针对富水中粗砂-风化岩复合地层易发生的刀盘结泥饼、螺旋输送机出渣喷涌等施工风险,设计防喷涌和防泥饼试验装置研究分散剂及膨润土泥浆的渣土改良效果;针对性地提出不同掘进平衡模式控制要点及“泡沫剂、分散剂为主,膨润土泥浆为辅”的渣土改良方法。研究结果表明:1)分散剂具备较好的防结泥饼能力,掺入比在4%时分散效果较佳;2)膨润土泥浆可有效改善砂土流动性,掺入比在10%、黏度大于80 s时具有较好的改善效果;3)采用泡沫、分散剂、膨润土组合进行渣土改良,合理控制土舱内渣土舱位,可较好适应土压平衡模式在中粗砂-风化岩复合地层掘进。

To examine the construction adaptability of dual-mode shield(earth pressure balance mode and slurry balance mode)tunneling in medium coarse sand-weathered rock composite strata under earth pressure balance mode,a case study is conducted on the tunnel section between Chishajiao station-Luntou station of the Guangzhou metro line 12.Due to the construction risks of shield tunneling in medium coarse sand-weathered rock composite strata,i.e.,mud cake on cutterhead and mud gushing of screw conveyor,anti-gushing and anti-mud cake test devices are designed to examine the soil conditioning effect by dispersants and bentonite slurry.Finally,the control points of shield tunneling under various modes are proposed,providing the soil conditioning method of"foam agent and dispersant based,supplemented by bentonite slurry".The research results indicate the following:(1)Dispersants can effectively prevent the cutterhead from mud cake,and 4%dispersion content is the optimal.(2)Bentonite slurry can effectively improve the flowability of sand,with a good improvement effect when the addition ratio is 10%and the viscosity is greater than 80 s.(3)By conducting soil conditioning while keeping a rational soil level in soil chamber can achieve safe and efficient tunneling in medium coarse sand-weathered rock composite strata.