沉管隧道格形地墙护岸变形的地层参数敏感性分析

Sensitivity Analysis on Stratum Parameters of Latticed Diaphragm Wall Revetment for Immersed Tunnel

岩土体参数的不确定性是困扰地下工程设计分析的一大难题,可在数值模拟中通过参数敏感性分析的方法加以研究。如意坊放射线隧道工程(一期工程)沉管护岸采用格形地下连续墙的支护形式,其结构性态复杂,受力变形性质相比传统支护结构存在明显的差异。在进行方案设计时,通过建立大型三维有限元模型,模拟沉管隧道基槽的开挖过程,揭示了格形地墙的变形模式,分析了地层参数不确定性的影响。数值模拟结果显示:开挖卸载会导致格形地墙发生向江侧的倾斜,一级基槽边坡开挖后,地墙最大侧移约为14.1 mm(最大开挖深度H的1.64‰),二级基槽边坡开挖后,地墙的最大侧移约为23.8 mm(1.74‰H),表明现有设计方案能够有效控制施工扰动;在基岩埋深,土体强度和模量3个分析因素中,地墙护岸变形对基岩埋深的变化最为敏感,基岩埋深越深,相应的地墙嵌岩长度越短,开挖卸荷引起的变形越大;减小土体模量和强度时,地墙变形明显增大,而增大土体参数对计算结果的影响较小。因此在勘探和设计时,须进一步完善测试技术和增强数据分析能力,提高岩土参数的准确性,其中应尤其重视对基岩埋深的分析。研究得到的格形地墙三维变形模式及对地层参数的敏感性,可为设计和施工提供参考建议,对类似工程也有很好的借鉴价值。

The uncertainty of geotechnical parameters is a big problem that troubles the design and analysis of underground engineering,which can be studied by parameter sensitivity analysis in numerical simulation.The immersed tunnel revetment of Ruyifang radiation tunnel project(Phase I)adopts the support form of lattice diaphragm wall,its structural state is complex,and the stress and deformation properties are significantly different from the traditional support structure.During scheme design,by establishing a large 3D FE model,the excavation process of the foundation trench is simulated,the deformation characteristics of the lattice diaphragm wall is revealed,and the stratum parameter uncertainty is discussed.The result of numerical simulation shows that(1)Excavation and unloading will cause the diaphragm wall to incline to the river side.After the excavation of the first-level trench,the maximum lateral displacement of the diaphragm wall is about 14.1 mm(1.64‰of the maximum excavation depth H),for the second-level trench,the value is about 23.8 mm(1.74‰H),showing that the existing design scheme can effectively control the construction disturbance.(2)Among the analysis factors of bedrock depth,soil strength and modulus,the deformation of the diaphragm wall revetment is most sensitive to the change of bedrock depth.The deeper the bedrock depth,the shorter the corresponding embedded length of the diaphragm wall,and the greater the deformation caused by excavation unloading.(3)When the soil modulus and strength are reduced,the deformation of the diaphragm wall increases significantly,whereas increasing the soil parameters has little influence on the calculation result.Therefore,during exploration and design,it is necessary to further improve the testing technology and enhance the data analysis ability to improve the accuracy of geotechnical parameters,especially the analysis of bedrock depth should be paid special attention.(4)The studied 3D deformation mode of the lattice diaphragm wall and its sensitivity to stratum parameters can provide reference suggestions for design and construction,and also have good reference value for similar projects.