考虑纵向变形影响的基坑下方盾构隧道横向受力变化研究

Research on transverse force and deformation of shield tunnels below foundation pits considering influence of longitudinal deformation

针对基坑开挖引起下方盾构隧道围压变化的机制进行分析,提出一种能考虑纵向变形影响的盾构隧道横向附加围压变化模型。建立盾构隧道管片环的有限元简化模型,进行结构计算分析。以基坑上跨杭州地铁1号线盾构隧道为例,将隧道水平收敛计算值与实测数据进行对比,验证了计算方法的可靠性。研究基坑下方盾构隧道的围压变化、衬砌内力以及纵横向受力关系,并对基坑空间开挖尺寸进行影响因素分析。研究结果表明:计算得到的隧道水平收敛变形值及其沿隧道纵向的分布规律与实测值基本吻合;基坑开挖引起的围压卸载效应主要作用于下方隧道衬砌的拱顶和拱底附近,并受纵向变形过程中环间作用力的影响;基坑开挖导致下方盾构隧道衬砌弯矩分布反转,拱腰处的轴力也显著减小;三维卸载比V3D可以较好地反映基坑空间开挖尺寸对下方盾构隧道的影响。

Based on the analysis of confining pressure variation of shield tunnels caused by foundation pit excavation,a model for evaluating the transverse additional confining pressure of shield tunnels,considering the influence of longitudinal deformation,is proposed. A simplified finite element model of shield tunnel segment rings is established for structural calculation and analysis. Taking a underlying shield tunnel of Hangzhou metro line 1 as an example,the calculated values of the horizontal convergence of the tunnel is compared with the measured data to verify the reliability of the calculation method. The confining pressure,the internal force of linings and the relationships of the longitudinal and transverse forces are studied,and the influence of the excavation size of the foundation pit is analyzed. The results prove that the calculated horizontal convergent deformation of the underlying tunnel and its distribution along the tunnel well match the measured values. The unloading effect of the confining pressure caused by excavation mainly affects the top and bottom of the tunnel lining and is affected by the forces between segments in the process of longitudinal deformation. The excavation causes the reverse of the bending moment on the shield tunnel lining and significantly reduces the axial force at the arch waist. The three-dimensional unloading ratio V3 D can better reflect the influence of the size of the excavation on the underlying shield tunnel.