渗流作用下盾构隧道地表变形规律研究

Research on Surface Deformation Law of Shield Tunnel under Seepage

在泥水平衡盾构工法中,通常会用密封舱的泥浆来平衡开挖面的水土压力,从而达到控制地表变形的目的,因此,泥浆压力的选取十分关键。为了解决工程中泥浆压力的选取问题,采用理论分析方法,结合泥水盾构隧道开挖面平衡稳定原理,对泥浆在开挖面上的3种形态进行对比分析,结果表明,“渗透模型”在工程中广泛存在,且渗透作用会导致开挖面稳定性减弱。基于“渗透模型”,采用FLAC^(3D)软件进行流固耦合计算,结果显示,渗流作用下地表最大沉降随泥浆压力的增大而减小,当泥浆压力达到一定限值后(本工程背景下为400 kPa),地表最大沉降值不再减小,该研究解决了合理确定泥浆压力控制地表沉降的难题;通过分析盾构掘进过程中岩土体应力状态分区和地表沉降云图,构建了地表沉降范围预测模型,模型理论计算结果与数值模拟结果吻合良好,该模型可用于泥水盾构隧道施工引起的地表沉降范围预测。此外,在泥浆压力为400 kPa时,采用数值计算方法进行了泥浆渗漏计算,结果表明泥浆渗漏上边界距水库底面7.5 m,不会对保护区水体造成污染。该研究结果可为泥水平衡盾构施工中泥浆压力的选取、地面沉降范围的确定以及泥浆渗漏的影响这3个施工难题提供解决思路。

In the slurry balance shield method,the slurry from the sealed chamber is usually used to balance the water and soil pressure on the excavation surface,so as to control the surface deformation.Therefore,the selection of slurry pressure is very important.In order to solve the problem of selecting the slurry pressure in the project,this paper uses the theoretical analysis method to compare and analyze the three forms of slurry on the excavation face,in combination with the principle of balance and stability of the slurry shield tunnel excavation face.The results show that"seepage model"widely exists in engineering,and the seepage effect will weaken the stability of excavation face.Based on the"seepage model",the fluid-structure coupling calculation is carried out by FLAC^(3D) software.The results show that the maximum surface settlement under the effect of seepage decreases with the increasing of mud pressure.When the mud pressure reaches to a certain limit value(400 kPa in the background of this project),the maximum surface settlement value will not decrease.This study solves the problem of how to reasonably determine the mud pressure to control the surface settlement.Based on the analysis of the stress state zoning of rock and soil and the surface settlement nephogram during shield tunneling,a prediction model of the surface settlement range is established.The theoretical calculation results of the model are in good agreement with the numerical simulation results.The theoretical calculation result of this model meets with the numerical simulation result.The model can be used to predict the surface settlement range caused by slurry shield tunneling.In addition,when the mud pressure is 400 kPa,the numerical calculation method is used to calculate the mud leakage in this paper.The results show that the upper boundary of the mud leakage is 7.5 m away from the bottom of the reservoir and will not pollute the water body in the protection area.The research results of this paper can provide solutions to three construction problems,namely,the selection of slurry pressure during slurry balance shield construction,the determination of the range of ground settlement and the impact of slurry leakage in slurry balance shield construction.