墩台基坑开挖过程中列车动载对路堤的动变形分析

大量新建桥梁桥墩基坑工程位于铁路路基保护范围以内,使得铁路不可避免地受到基坑开挖的影响,既有铁路的列车动载加剧这种不良影响。在基坑开挖过程中,为了确保邻近铁路的安全,以孙渡特大桥上跨丰洛铁路桥墩施工为背景,通过建立三维有限元数值模型,分析在客车和货车不同速度下邻近既有线的基坑开挖过程中路堤的动变形规律:随着基坑不断向下开挖,路基中心处的竖向动位移和水平向动位移均增大,且水平动位移增长率大于竖向动位移增长率。60 km/h客车和40 km/h货车动荷载下路基中心的竖向最大动位移分别为3.32 mm和3.42 mm,其他情况均大于3.5 mm。最后基于铁路路基动变形3.5 mm的控制标准,提出在基坑开挖过程中客车限速60 km/h和货车限速40 km/h的控制措施可行。

Dynamic Deformation Analysis of Train Moving Load on Embankment during Excavation of Pier Foundation Pit

A large number of new bridge pier foundation pit engineering projects are located within the scope of railway subgrade protection,making the railway inevitably affected by the excavation of the foundation pit and the train dynamic load exacerbates the adversity. To ensure the safety of the adjacent railway in the process of foundation pit excavation,a three-dimensional finite element numerical model is established to analyze the dynamic deformation of embankment during the excavation of foundation pit adjacent to existing railway line subject to passenger cars and freight car at different speeds with reference to the construction of bridge piers of Sun Du extra-long bridge. With downward vertical pit excavation,the roadbed center displacement and horizontal displacement are all increased,and the level of displacement is greater than the growth rate of vertical displacement of growth rate. The subgrade center vertical maximum displacement are respectively 3. 32 mm and 3. 42 mm under 60 km/h car and 40 km/h wagon loads,and it is more than 3. 5 mm for other cases. Finally,the control limit of 3. 5 mm railway subgrade dynamic deformation in the process of foundation pit excavation subject to speed limit of 60 km/h passenger car and 40km/h freight car is proved applicable.