移动列车作用下大直径顶管群和路基的动力变形和应力

大直径顶管下穿重要铁路干线时,路基的承载力和动力特性必将发生改变,铁路部门要求列车运行时顶管上方竖向动位移与顶管施工前相比变化量≤5 mm。对列车驶过顶管群上方铁路的过程进行了数值模拟,给出路基瞬时竖向位移和顶管附加动应力等结果。采用三维有限元Newmark动力时程分析法和seed等效线性法模拟路基的振动软化,按照实际工程考虑6根直径4.7 m的顶管群下穿京沪铁路,计算列车速度分别为100,200 km/h。计算结果表明,在管道埋深12 m时,路基最大竖向动位移增加1.3 mm,顶管受到的附加拉(压)动应力为0.14 MPa左右,顶管群对铁路运行的影响在容许范围内。

Dynamic Deformation and Stress of Large-diameter Pipe Jacking Passing underneath Railway Subgrade under the Action of Moving Train

The bearing capacity and dynamic characteristics of railway subgrade are bound to change in the presence of large-diameter pipe jacking passing underneath. The increment of vertical dynamic displacement above the pipe jacking should be within 5 mm, according to railway administrations. The process of train passing on the pipe jacking is numerically simulated. The instantaneous vertical displacement of subgrade and the additional dynamic stress of pipes are given. Newmark dynamic analysis method in association with Seed's equivalent linear method is employed to simulate the vibrational softening of subgrade. The simulation scenario is designed as a pipe jacking group composing six pipes of 4.7 m diameter passing underneath the Beijing-Shanghai railway, with the velocity of train reaching 100 km/h and 200 km/h respectively. When the pipes are buried at a depth of 12 m, the maximum vertical dynamic displacement of subgrade is 1.3 mm, and the additional tensile/compressive stress of pipes are around 0.14 MPa, within in allowable range.