地下水路堑段槽型挡土墙设计若干问题的探讨

对于地下水路堑段槽型挡土墙,铁路设计人员一般采用边墙简化为悬臂梁、底板简化为弹性地基梁的结构计算模型。一个整体结构简化为两个分离的构件,计算模型本身存在一定的缺陷,一些设计者对此不甚了解;在边墙土压力计算理论的选择、边墙外侧活荷载侧压力的计算、抗浮措施的确定、抗浮稳定安全系数的选取、地基压缩模量的选用等方面也存在疑惑。通过多个荷载组合工况的内力及位移计算,结合国内外标准的有关规定,探讨了结构计算模型的合理性以及弥补其缺陷的措施,提出了设计参数选取的优先方向,得出如下结论:在地下水位较高时,弹性地基梁链杆出现负反力是其最大的缺陷;边墙位移小于产生主动土压力所需位移,土压力计算采用静止土压力更为合理,同时可以减小链杆负反力,弥补弹性地基梁模型缺陷;边墙外侧活荷载宜按非主可变荷载单独计算其侧压力,不宜合并入土压力;抗浮优先考虑底板外延方式;抗浮系数在限制结构重要性系数不小于1.0的条件下取1.05;弹性地基梁模型对地基压缩模量取值不敏感。

Discussion on the Design of Groove Retaining Wall with Underground Water

For groove retaining wall in groundwater cutting section, railway designers usually simplify the side wall to cantilever beam and the floor to elastic foundation beam. On one side, a whole structure is simplified into two separate members, it must has some defects, which some designers do not know much about; on the other hand, there are doubts in other aspects, such as the selection of calculation model of soil pressure on side wall, the calculation of lateral pressure on side wall under live load, the determination of anti-floating measures, the selection of safety factor of anti-floating stability, and the selection of compressive modulus of foundation. Based on the calculation of internal forces and displacements under multiple load combinations, and the relevant provisions of domestic and foreign standards, this paper discusses the rationality of the calculation model and the measures to remedy its defects, puts forward the priority direction of selecting design parameters, and draws the following conclusions: when the groundwater level is high, the negative reaction of the elastic foundation beam chain rod is the biggest defect; displacement of side wall is less than that needed to produce active soil pressure, so it is more reasonable to calculate static soil pressure, at the same time, the loading of static soil pressure can reduce negative chain reaction and make up for the defects of the elastic foundation beam model; lateral live load of side wall should be calculated separately according to non-principal variable load, and it is not suitable to merge into earth pressure; base plate extension is prioritized for floating resistance; floating resistance coefficient of 1.05 is taken when the structural importance coefficient is not less than 1.0; the elastic foundation beam model is not sensitive to the value of compressive modulus of foundation.