深水基础大规模超长钢板桩围堰施工过程安全性分析

Analysis on Safety during Construction Process for Large-Scale and Super-Long Steel Sheet Pile Cofferdam of Deepwater Foundation

以阜阳至六安铁路颍河特大桥主墩深水基础超长钢板桩围堰施工为例,考虑钢板桩、内支撑和周围土体相互作用,运用ANSYS软件,建立其三维整体有限元模型,分别对静水和流水条件下超长钢板桩围堰施工过程进行力学行为及安全性分析。结果表明:钢板桩桩身水平位移随着工序的推进不断增大,最大水平位移位于基坑开挖面附近;每道内支撑最大轴向应力出现在该道内支撑施工完成以后的第1个抽水吸泥工序,并随工序的推进而波动变化;施工过程中应该特别注意最后2个工序的施工安全;流水压力对钢板桩围堰的影响主要体现在迎水面的钢板桩桩身水平位移有所增大;基底抗隆起和围堰整体抗倾覆安全系数均满足相关规范要求,施工过程结构是安全的。

A case study was done for the super-long steel sheet pile cofferdam construction practice of the main pier deepwater foundation at Ying River super major bridge of Fuyang-Lu＇an Railway. Three-dimen- sional finite element model was established by ANSYS software considering the interactions among steel sheet pile, internal bracing and surrounding soil mass. The mechanical behaviors and safety were analyzed during construction process by simulation analysis for super-long steel sheet pile cofferdam under still wa- ter and running water conditions respectively. The results show that the horizontal displacement of steel sheet pile increases constantly with the driving on of construction procedures, and the position of maximum horizontal displacement is located next to the excavation face of foundation pit. The maximum axial stress of each internal bracing appears at the first construction procedure of water pumping and mud suction after its installation, and it fluctuates with the advancement of construction procedures. The construction safety of the last two procedures should be paid special attentions during construction process. The influence of running water pressure on steel sheet pile cofferdam is mainly embodied in that the horizontal displacement of steel sheet pile at upstream face has somewhat increased. Both the safety factors of resistant heave sta- bility for excavation and whole overturning resistance for steel sheet pile cofferdam meet the demand of rel- evant standards. The structure of steel sheet pile cofferdam is safe during construction process.