异形板桥桩基托换力学行为及变形规律研究

Research on mechanical behavior and deformation law of pile foundation underpinning of special shaped slab bridge

随着地铁建设的迅速发展,不可避免的穿越既有城市立交桥,对其沉降及受力状态产生重大影响。依托石家庄地铁2号线下穿建和桥桩基托换工程,利用有限元软件,建立三维有限元模型,实现了桩基托换全过程模拟,通过数值计算得出了沉降变化规律,并与现场实际数据进行了对比分析。沉降结果表明,建和桥南桥托换部位沉降较大,应加强此区域位置的监控。通过分析桥面异形板及桩基应力历史,得出:桥面异形板在施工过程中应力变化主要集中在断桩施工阶段;原始桩基在托换施工全过程中,受力表现出先减小后增大的变化规律,新建桩基有效应力呈现出持续增长的现象;断桩施工将原始桩基受力有效转移至新建桩基,盾构施工对各结构应力状态影响较小。

With the rapid development,subway construction is inevitable to pass through existing urban overpasses,which will significantly impact its settlement and stress state.This research relies on the underpinning engineering of pile foundations of Jianhe bridge passed by Shijiazhuang Metro Line 2.Using finite element software,a three-dimensional finite element model is established,and the whole process of pile foundation underpinning is simulated.The settlement change rule is obtained through numerical calculation and compared with the field data.The results show that the settlement is large in the underpinning position of South Jianhe Bridge,in which the monitoring should be strengthened.Finally,the stress history of the special-shaped slab on the bridge deck and the pile foundation is analyzed,and the laws are as follows.The stress changes of the special-shaped slab on the bridge deck are mainly concentrated in the construction stage of the pile breaking.In the whole process of underpinning construction,for the original pile,the forces show a change law of first decreasing and then increasing,while the effective stress of the newly-built pile foundation showed a continuous increase.The pile-breaking construction effectively transfers the force of the original pile foundation to the newly-built pile foundation,and shield construction has little effect on the stress state of each structure.The results can provide references for the design and construction of similar underpinning projects of pile foundation.