公路桥上跨地铁微变形控制技术数值模拟分析

Numerical Simulation Analysis on Micro-deformation Control Technology of Highway Bridge over Subway

针对公路桥上跨地铁施工工程中的微变形控制专项技术,研究了高架桥桩基础施工全过程对邻近已有地铁隧道变形的影响,进而为工程施工提供了可靠的参考依据,保证已运营地铁隧道的正常运行。首先选用Winkler地基模型与周围土体耦合求解了已有地铁隧道的隆起变形,然后采用有限元方法计算了高架桥桩基础施工过程中不同阶段邻近地铁隧道的变形,并针对有无搅拌桩施工工况进行了对比分析。最后根据专项施工方案中搅拌桩弹性模量、钢护筒厚度以及桩基础周边土体性质进行了广泛的参数分析。结果表明:对于无搅拌桩工况,通过理论计算模型和有限元数值模拟结果的对比验证了数值模型的准确性,搅拌桩的施工可以有效地降低邻近地铁隧道水平向和竖直向的位移变形,尤其是竖直向的微变形控制效果更佳;搅拌桩弹性模量的大小直接关系到桩基础的施工对周围土体的变形影响,桩周土体弹性模量较小时需增大搅拌桩弹性模量,从而减小桩基础开挖对邻近地铁隧道的变形影响;钢护筒的厚度对邻近地铁隧道的影响主要体现在水平位移上,对竖直向变形影响较小;桩周土体越软弱,专项施工方案的作用越显著,反之,桩基础施工对邻近地铁隧道的变形控制要求可适当降低。

Aiming at the special technology of micro-deformation control in the cross-metro construction work of highway bridge, the influence of the whole construction process of viaduct pile foundation on the deformation of adjacent existing subway tunnel is studied, so as to provide a reliable reference for engineering construction and ensure the normal operation of the existing subway tunnels in operation. First, the uplift deformation of the existing subway tunnel is solved by using the Winkler foundation model coupling with the surrounding soil. Then, the deformations of the adjacent subway tunnel at different stages during the construction of the viaduct pile foundation are calculated by using the finite element method, and the construction working conditions with and without mixing pile are compared and analyzed. At last, the parameters are extensively analyzed according to the elastic modulus of mixing pile, the thickness of steel cylinder and the properties of soil around the pile foundation in special construction scheme. The result shows that(1) The accuracy of the numerical model is verified by comparing the results of the theoretical calculation model and the finite element numerical simulation for the working condition without mixing pile. The construction of mixing pile can effectively reduce the horizontal and vertical displacement deformations of the adjacent subway tunnel, especially for the vertical micro-deformation control effect.(2) The elastic modulus of mixing pile is directly related to the influence of the pile foundation construction on the deformation of surrounding soil. When the elastic modulus of soil around the pile is small, the elastic modulus of mixing pile should be increased to reduce the influence of deformation of pile foundation excavation on the adjacent subway tunnel.(3) The influence of thickness of steel cylinder on adjacent subway tunnel is mainly reflected in horizontal displacement but has little influence on vertical deformation.(4) The weaker the soil around the pile is, the more significant the effect of the special construction scheme is. Conversely, the deformation control requirements of pile foundation construction on adjacent subway tunnel can be reduced appropriately.