带衬砌浅埋隧道开挖受非对称收敛变形影响的地层位移和衬砌应力分析

Elastic analysis of ground displacement and liner stress induced by shallow shield excavation considering non-uniform convergence deformation with liner

盾构隧道施工引起的环境土工效应分析一直是城市轨道交通安全控制的关键课题。由于目前该领域较少考虑隧道衬砌与土体相互作用带来的影响,尤其是较少针对衬砌应力进行分析,由此提出带衬砌浅埋隧道开挖受非对称收敛变形影响的地层变形计算方法;同时考虑地层与衬砌之间的非对称收敛协调变形模式,建立带衬砌隧道开挖的Airy应力函数解析解答。通过实例研究,得到带衬砌隧道非对称变形模式下的地层沉降和水平位移曲线,并与实测数据进行对比验证;通过参数分析,获取土体和衬砌的材料特性、隧道几何特性以及隧道埋深等主要参数对浅埋隧道开挖地层变形和衬砌应力的影响规律。结果表明:非对称收敛变形模式对地层位移的影响明显,在此条件下得到的沉降槽和水平位移曲线与实测值吻合较好,地表最大沉降值更接近于实际;隧道半径或土层硬度对土体沉降最大值有较大影响,减小半径和硬化土层对减少土体沉降量效果显著,而衬砌几何参数的改变对沉降量的影响不大;衬砌轴力和弯矩整体关于90°/270°轴即隧道竖轴线严格对称,其中轴力沿圆周呈倒"8"字分布,而弯矩随着k值的增大,沿圆周方向由"8"字形向"0"字形过渡,最大轴压力和最大负弯矩发生在拱腰位置,土体侧压力系数k的取值对衬砌轴力和弯矩的分布和大小影响明显。分析成果可为正确预估软土浅埋盾构开挖变形提供一定的理论依据。

The geo-environmental effects caused by shield tunneling have been a key issue in urban metro construction. However, few investigations have been carried on the impacts of interaction between tunnel liner and soils. Particularly, the stress analysis of the liner is not conducted. A calculation method for soil displacements affected by tunneling with liner was proposed considering the non-uniform convergence deformation. The Airy stress function analytical solution of tunnel liner was established considering the compatibility of non-uniform convergence deformation between liner and soils. The stratum subsidence and horizontal displacement curves of soils from calculation were compared with the monitoring data. The influence of the material properties of soil and liner, the geometry and depth of tunnel and other main parameters on ground deformation and liner stress induced by tunneling were obtained through the parameter analysis. The non-uniform deformation mode was found to significantly affect the ground displacements. The soil settlements and horizontal displacement curves were in good agreements with the measured values. The maximum value of the surface settlement is close to the actual one. The tunnel radius and soil hardness have greater effects on the maximum subsidence of soils. Soil subsidence was reduced significantly by decreasing the radius and hardening soil. Change of the geometric parameters of liner has little effects on the soil settlements. The axial force and bending moment of liner are strictly symmetrical to axis of 90 °/270° or tunnel vertical axes. The distribution of axial force along the circumference has the shape of 8. The shape of bending moment distribution was changed from 8 to 0 along the circumference with the increase of parameter k. The maximum axial stress and maximum negative moment occur in the position of arch lumbar. The values of lateral earth pressure coefficient k affect significantly the axial forces and bending moments of liners.