截污管道水下基槽钢板桩围堰施工数值模拟分析

Numerical Simulation Analysis of Steel Sheet Pile Cofferdam Construction for Underwater Sewage Interceptor Trench

以云南省昆明市滇池草海段截污管线埋置工程为背景,采用MIDAS/GTS NX有限元软件建立水下基槽钢板桩围堰二维数值模型。分析对比基槽在改变拉森钢板桩桩长、开挖排水情况下所设置的四种开挖方案中,基槽坑顶水平位移、坑底隆起(回弹)变形量的变化规律。结果表明:通过增加拉森钢板桩桩长和采用不排水的基槽开挖方式,在控制坑顶水平位移量、坑底隆起(回弹)变形量上总体呈收敛状态,但基槽变形量不能达到基坑二级安全等级要求。鉴于该情况,对开挖方案进一步优化设计,在基槽底部施作厚度为0.8 m的碎石垫层,能够有效降低坑顶水平位移量、坑底隆起(回弹)变形量;钢板桩围堰的坑顶水平位移量为负值,要求施工中应加强内支撑与横梁,横梁与钢板桩的连接。

Against the backdrop of the sewage interception pipeline burial project in the Caohai section of Dianchi Lake in Kunming,a two-dimensional numerical model of the underwater steel sheet pile cofferdam was established using MIDAS/GTS NX finite element software.The study involved analyzing the changes in horizontal displacement of the cofferdam top and the amount of bottom uplift(rebound)deformation under four construction conditions with varying Larson steel sheet pile lengths and excavation drainage.The results indicate that increasing the Larson steel sheet pile length and using a non-draining excavation method for the cofferdam led to an overall convergence in controlling the trench top horizontal displacement and bottom uplift(rebound)deformation.However,the deformation of the cofferdam still did not meet the second-level safety requirements for the foundation pit.In light of this situation,an optimization of the excavation conditions was conducted,involving the placement of a 0.8mthick layer of crushed stone at the bottom of the cofferdam.Finite element numerical simulations demonstrated that this method effectively reduces the trench top horizontal displacement and bottom uplift(rebound)deformation.