横向管幕对洞桩法车站施工形变的影响研究

Impact Study of the Horizontal Pipe-Roof on PBA Method Station Deformation

目前管幕洞桩法施工的地铁车站多采用管幕与车站方向一致的纵向管幕洞桩法,而横向管幕洞桩法较少。以北京地铁19号线右安门外站为背景,介绍了管幕结构、导洞设计及洞桩设计方案,在有限元模拟基础上,对比了不同管幕工况下车站施工变形特征。研究表明:无管幕工况下横向影响范围为车站中心向外一倍车站跨度,管幕工况下影响范围有所减小,单侧减小2 m左右;先行导洞施工纵向影响范围约为四倍导洞跨度;管幕工况下后行导洞上方地表沉降小于无管幕工况,地表沉降控制明显;管幕对先行导洞初支位移影响很小,对后行导洞初支位移控制明显;管幕施工明显削弱先行导洞结构,需采取加强措施。本研究可为类似工程设计与施工提供借鉴与参考。

At present, the longitudinal pipe-roof PBA method, in which the direction of pipe-roof is consistent with the longitudinal direction of subway station, is widely adopted in subway station by pipe-roof PBA method. While the horizontal pipe-roof PBA method is rarely carried. Taking Youanmenwai Station of Beijing Subway Line 19 as the background, pipe-roof structure, drift design and cave-pile design are introduced. Based on 3D FEM simulation, the deformation characteristics of subway station construction under different pipe-roof conditions are compared. Some conclusions have been drawn. Firstly, the horizontal influence range is the station span from the station center under no pipe-roof condition. the horizontal influence range under no pipe-roof condition is reduced about 4 m. Secondly, the longitudinal influence range of advance drift is about 4 times of the drift span. Thirdly, the surface settlement above the post drifts of pipe-roof condition is smaller than that of no pipe-roof condition. Therefore, the pipe-roof has an obvious control effect for surface settlement. Fourth, the pipe-roof has little influence on the primary-support displacement of the advance drift. And the displacement control on the primary-support displacement of the post drifts is very obvious. Finally, the pipe-roof construction has a great weakening effect on the advance drift and structural strengthening measures need be proposed. The experience can be used in design and construction of similar projects.