车站异形深大基坑施工过程试验研究

研究目的:异形深大基坑施工过程的稳定性一直是工程界研究的热点和难点问题,为探究异形深大基坑施工过程中支护结构变形演化规律和受力特征,本文以某大型异形深基坑为依托,开展支护结构变形和受力现场试验研究,以期为依托工程和类似工程设计施工提供指导。研究结论:(1)异形深大基坑支护结构变形的空间效应显著,异形段的墙顶水平位移大于标准段;(2)地下连续墙的水平位移两头小、中间大,随深度增加呈三角形分布,位移最大处发生在基底±3 m附近;支撑处墙体位移较小,外荷载、施工中断会使墙体位移增大;(3)当基坑深度小于15 m时,支护结构土压力分布规律接近朗肯土压力理论值;当基坑深度大于15 m时,支护结构土压力明显小于朗肯土压力理论值,按理论计算值指导设计施工偏于保守;(4)异形深大基坑施工建议采取"地下连续墙+钢筋混凝土支撑+钢支撑"的组合支护形式,可有效控制支护的过大变形;(5)本研究成果可为基坑工程施工提供参考和借鉴。

Field Test Research on the Construction Process of Special-shaped Deep and Large Foundation Pit of Station

Research purposes: The stability construction process of special-shaped deep large foundation pits has always been a hot and difficult point in the engineering field. In order to explore the deformation law and stress characteristics of its supporting structure during the construction,based on a special-shaped deep large foundation pit,the paper carried out field test research on deformation and stress of supporting structure,to provide guidance for the design and construction of relying on projects and similar projects.Research conclusions:( 1) It is greatly affected by the spatial effect that the deformation of the special-shaped deep large foundation pit support structure. The horizontal displacement of the wall top at the special section is more than that of the standard section.( 2) The horizontal displacement of the diaphragm wall is less at both ends and larger at the middle. As the depth increases,the deformation presents triangular shape,and the maximum displacement occurs near± 3 m at the base. The horizontal displacement of the wall at the support is small,and the external load and construction interruption will lead to the increase of wall horizontal displacement.( 3) When the depth of the foundation pit is less than 15 m,the distribution law of earth pressure of the supporting structure is close to the theoretical value of Rankine earth pressure;when the depth of the foundation pit is greater than 15 m,the earth pressure of the supporting structure is significantly less than the theoretical value of Rankine earth pressure,and it is conservative to guide the design and construction according to theory value.( 4) It is recommended to adopt the combined supporting form of " diaphragm wall + reinforced concrete support + steel support" for the construction of special-shaped deep large foundation pit,which can effectively control the excessive deformation of the support.( 5) The research results can provide reference for the construction of foundation pit engineering.