地表交通荷载引起邻近浅埋隧道振动评价研究

为研究地表交通荷载引起邻近浅埋隧道振动问题,建立地表移动荷载下三维弹性半空间中隧道振动分析模型。隧道衬砌模拟为中空圆柱体,隧道周围土体模拟为含有圆柱形空腔的黏弹性半空间。地表车辆荷载简化为4个均布矩形荷载,矩形荷载可以分解为关于隧道轴线正对称和反对称2种荷载分量。含有圆柱形孔洞的地基中位移场分解为下行平面波引起的位移场和外行圆柱波引起的位移场,通过波场转换可对地表和衬砌–土体接触处的边界条件进行描述,在频域中获得控制方程基本解,然后利用快速Fourier变换获得时域结果求得。地表车辆荷载下邻近隧道的振动响应可由正对称和反对称荷载工况下的结果叠加得到。计算结果表明:隧道两侧车辆荷载在隧道处引起径向动应力最大值分布在以竖向为中心的-45°~45°范围;增加隧道埋深或车辆距隧道的水平距离,可显著减小隧道的振动速度响应和应力响应;一定隧道埋深下,车辆荷载与浅埋隧道的水平距离达到最小安全距离时隧道振动可以满足相关振动规范的要求,且该安全距离跟车辆速度在研究范围内呈线性关系。

Evaluation of shallow tunnel vibration caused by adjacent surface traffic loads

In order to study the vibration of shallow tunnels caused by adjacent surface traffic loads,a threedimensional vibration prediction model for shallowly-buried tunnels generated by a moving surface loading was established,where the lining is simulated as a circular cavity and the ground around the tunnel is modeled as a viscoelastic half-space with a circular cavity. The vehicle load is represented by four rectangular pressures,which can be decomposed into symmetric and antisymmetric components with respect to the tunnel axis. The displacement field of the ground with a circular cavity is decomposed into the displacement fields respectively caused by the down-going plane wave and the outgoing cylindrical wave. The boundary conditions of soil-tunnel interface and ground surface are described through the transformation of plane and cylindrical waves,and the governing equations obtained from the frequency domain can be solved based on the time domain calculated by quick Fourier transform. The vibration of the tunnel under the moving surface vehicle nearby can be obtained by superimposing the results in the symmetric and antisymmetric loading cases. The calculation results show that the maximum radial dynamic stress caused by the vehicle load is distributed between-45°and 45°around the vertical direction. Increasing the tunnel depth or the horizontal distance between the vehicle and the tunnel can significantly reduce the vibration velocity and stress response of the tunnel. Under a certain tunnel depth,the tunnel vibration can meet the requirement of specifications when the distance between the vehicle load and the shallow tunnel exceeds the minimum safety distance,and the safety distance has a linear relationship with the vehicle speed in the studied range.