曲线段大直径盾构掘进引发管片上浮影响

Influence of Segment Uplift Caused by Large-Diameter Shield Tunneling in Curved Sections

为研究曲线段大直径盾构隧道在上软下硬地层对管片上浮的影响,针对曲线段盾构隧道施工开挖面支护力、管片上浮的施工风险因素进行研究,采用极限平衡法研究开挖面支护力稳定性的影响,对开挖产生的不规则类棱台型土体进行横向竖向受力分析,建立静力平衡方程,求解开挖面处于极限平衡时的极限支护力.进一步研究开挖面支护力、曲线段大直径盾构隧道在上软下硬地层掘进对管片上浮的影响,并且分析影响管片上浮的地质以及盾构掘进姿态等因素,提出相应盾构管片上浮综合控制措施.结果表明:当破裂角φ_(1)=29.0°,φ_(2)=25.5°时,极限支护力T=128.5 k Pa.应合理控制盾构掘进姿态,保证合理的支护力,防止在上软下硬地层大直径盾构盾尾注浆滞后以及浆液硬化滞后,隧道产生偏离曲线掘进轴线的上下摆动,造成管片上浮;对于上浮比较严重的区域,可以采用双液注浆法,阻止管片上浮;对于已经产生管片上浮的区域,可以采取“上压下放”的方式增加隧道的配重或采用抗拔装置施加外力来抵抗地下水上浮量.

In order to study the influence of the large-diameter shield tunnel in the curved section on the floating of the segment in the upper soft and lower hard strata,the support force of the excavation surface and the construction risk factors of the floating segment of the shield tunnel in the curved section were studied.The limit equilibrium method was used to study the influence of the excavation face support force stability.The horizontal and vertical force analysis was carried out on the irregular prism-like soil produced by the excavation,and the static equilibrium equation was established to solve the limit support force when the excavation surface is in limit equilibrium.Further research was done on the support force of the excavation face and the influence of the large-diameter shield tunnel in the curved section on the rise of the segment in the upper soft and lower hard strata.In addition,the influencing factors such as the geology and the shield tunneling attitude that affect the rise of the segment were analyzed,and the corresponding comprehensive control measures for the rise of the shield segment were proposed.The results show that when the rupture angle isφ_(1)=29.0°andφ_(2)=25.5°the ultimate support force is T=128.5 kPa.Reasonably control the shield tunneling attitude,ensure reasonable support force,and prevent the lag of grouting and slurry hardening in the large-diameter shield tail of the upper and lower hard strata.The tunnel oscillates up and down deviating from the curved driving axis,causing the segment to float up.For areas with severe floating,the double-liquid grouting method can be used to prevent the segment from floating.For the range where the segment has floated up,the method of"pressing up and down"can be used to increase the counterweight of the tunnel or use an anti-pull device to apply external force to resist the amount of groundwater floating.