南昌富水砂层盾构掘进地面沉降控制技术

GROUND SETTLEMENT CONTROL TECHNOLOGY FOR SHIELD TUNNELING OF RICH WATER SAND LAYER IN NANCHANG

南昌地铁富水砂层含水量大、渗透系数高、水补给快,地层塑流性差、摩擦阻力大,开挖面受扰动后易失稳、坍塌。盾构施工渣土改良效果不佳,盾构推进时螺旋机易喷涌,引起地面沉降甚至塌陷。施工时可以适量使用高分子聚合物防止螺旋机喷涌,加强施工管理,尽量保持盾构连续掘进。文中主要通过南昌地铁某个富水砂层区间施工中出现的地面沉降及塌陷情况,从优化盾构渣土改良及掘进参数,加强施工管理措施等方面,结合盾构掘进参数、监测数据及典型案例情况,分析总结出南昌地铁富水砂层盾构掘进渣土改良主要以泡沫+膨润土为主。泡沫原液配合比宜控制在3%,膨润土每环注入量5方左右,盾构掘进速度宜控制在30~45mm/min、刀盘转速1~1.2r/min、总推力1000~1500T、刀盘扭矩2500~3500kN·m,可为类似地层盾构施工提供参考。

The water-rich sand layer of Nanchang Metro has large water content,high permeability coefficient,fast water recharge,poor formation plastic-flow property,and large friction resistance,which is prone to instability and collapse after the excavation face is disturbed.The slag improvement effect of shield construction is not good,and the screw is easy to gusher when the shield is advancing,causing the ground settlement and even collapse.During construction,high polymer can be used appropriately to prevent the spout of the screw machine,strengthen the con⁃struction management,and keep the shield continuous tunneling.Based on the ground settlement and collapse in the construction of a water-rich sand layer section of Nanchang Metro,this paper analyzes and concludes that the im⁃provement of shield dreg in water-rich sand layer of Nanchang Metro is mainly based on foam andbentonite fromthe aspects of optimizing the improvement of shield dreg and tunneling parameters.The mixture ratio of foam stock solu⁃tion should be controlled at 3%;the injection amount of bentonite in each ring should be about 5 square meters;the shield driving speed should be controlled at 30~45mm/min;the cutter head speed is 1~1.2r/min;the total thrust is 1000~1500T;the cutter head torque is 2500~3500kN·m,providing the reference for shield construction in similar strata.