列车振动荷载作用下明挖隧道施工过程中支护结构的动力响应分析

摘要

为了研究既有铁路沿线附近明挖隧道施工过程中支护结构的动力稳定性,结合FLAC3D软件分别采用列车静载和动载模型研究车致振动对周围自由场以及隧道基坑开挖施工的影响.主要结论如下: 1)采用列车静载模型所得结果小于动载模型的结果;2)车致振动以竖向分量为主,振动幅度沿水平向衰减很快,在距既有线6 m范围内衰减剧烈,之后趋于稳定;3)沿竖向衰减较慢,在20 m深度范围内,沉降量基本与深度呈二次曲线关系,之后趋于稳定;4)在既有线列车荷载作用下,不同施工阶段基坑底部总体有反拱趋势,为5~8 mm;5)采用锚索支护体系可以明显减小基坑侧壁的内倾变形.研究表明,既有线的列车荷载作用在水平方向上对于拟开挖隧道无明显振动影响,在竖向上当采用围护桩和锚索支护体系后可确保明挖隧道施工过程的整体稳定性.%The influence of train caused vibration on surrounding free field and tunnel foundation pit excavation is analyzed by static load model and dynamic load model respectively based on software FLAC3D.Some conclusions are drawn as follows: 1) The results from static load model are smaller than those from dynamic load model.2) The vertical components play one of the key roles in the train caused vibration load and its amplitude attenuates quickly along the horizontal direction;and the impact scope of vibration along horizontal direction is about 6 m.3) The impact scope of vibration along vertical direction is about 20 m, and the relationship between settlement of foundation pit and depth presents quadratic curve.4) The deformation of the foundation pit bottom during construction process presents inverted arch trend and its maximum value is about 5-8 mm.5) The anchor cable supporting technology can evidently reduce lateral deflection of the foundation pit wall.The study shows that after adopting the retaining piles and anchor cable supporting system, the whole dynamic stability of the cut-and-cover tunnel is not significantly affected by train caused vibration load on existing railway.