河床冲刷对桥梁桩基承载力影响及安全评价分析

The Effect and Safety Evaluation of Riverbed Scouring on Bearing Capacity of Bridge Pile Foundation

由于水库建设、疏浚、采砂及桥墩局部冲刷等影响,造成河床冲刷下切,桥梁桩基埋深减少,桩身外露、冲蚀损伤,影响桩基承载力及桥梁结构安全。分析河床冲刷对桩基承载力的影响,进行安全评估,对桩基管养决策和结构运营安全意义重大。本文以福州湾边特大桥为例,首先通过探摸检测和统计分析,探究河床冲刷和桩基混凝土冲蚀病害的形成机理;再采用Midas Civil有限元软件对河床冲刷和混凝土冲蚀病害对桩基承载力的影响进行数值分析,结果表明河床冲刷线及混凝土冲蚀对桩基竖向承载力影响较小,水平承载力影响较大,桩基仍处在安全状态;结合现有冲刷速度等情况,设置不同工况对桩基后续运营的安全性进行评估,提出了预警冲刷线和破坏冲刷线,为桩基的加固设计和管养决策提供指导。

Due to the detrimental influence of reservoir construction,dredging,sand mining and local scouring of bridge piers,the riverbed is deepened and undercut.As a consequence,the buried depth of the bridge pile foundation is reduced as well as the pile foundation is suffering erosion because of the exposure,which is unfavorable to the bearing capacity of the pile foundation and the safety of the bridge structure.The influence of the scouring of the pile foundation and its safety assessment is of great significance to the maintenance and management of the bridge.In this paper,a case study is performed on Fuzhou Wanbian Bridge.The formation mechanisms of the riverbed scouring and the pile foundation erosion are explored through manual detection and statistical analysis.Based on the Midas Civil platform,the influence of riverbed scouring and concrete erosion on the capacity of the pile foundation is analyzed.The results exhibit that the pile foundation is in safety,and the riverbed scouring and concrete erosion exert little impact on the vertical bearing capacity of the pile foundation,but more adverse effects on the horizontal bearing capacity of the pile foundation.In view of the current scouring speed,different scouring states of the pile foundation are analyzed and assessed.As a result,the warning and ultimate scouring lines are proposed,which provide guidance for the reinforcement design,management,and maintenance of pile foundations.