基于响应面法的基坑有限元模型修正

Modification of Finite Element Model of Foundation Pit Based on Response Surface Method

为建立适用于实际施工的高精度基坑有限元模型,提出一种基于响应面法的基坑有限元模型修正方法。首先以实际基坑为工程背景通过MIDAS GTS软件建立整个基坑开挖过程的有限元模型,以地表沉降、深层土体水平位移和内支撑轴力为因变量分别对各项参数进行敏感性分析,得到混凝土支撑的弹性模量、钢支撑与地连墙的弹性模量和密度并作为待修正参数。其次采用中心复合设计方法生成待修正参数的样本集,将各个样本集参数对应输入到有限元模型中进行计算,采用响应面法建立待修正结构参数和目标函数的二次多项式函数关系,最终得到优化后的修正参数。根据工程实例结果表明,修正后的有限元模型精度得到了一定程度的提高,与实测数据的精度误差能够保证在5%以内,可作为基准模型用于基坑的变形风险评估。

In order to establish a high precision finite element model of foundation pit,which is suitable for practical construction condition,a response surface method based finite element model modification method for foundation pit was proposed.Based on the actual foundation pit project a finite element model was established by MIDAS GTS software to simulate the whole excavation process,the sensitivity analysis of parameters was carried out by taking the surface subsidence,horizontal displacement of deep soil and axial force of internal strut as the dependent variable,and the elastic modulus of concrete support,the elastic modulus and density of steel support and diaphragm wall were determined as the correction parameters.Secondly,the central composite design method was used to generate sample sets of parameters to be modified,and the corresponding parameters of each sample set were input into the finite element model for calculation.Response surface method was used to establish the quadratic polynomial function relationship between the structural parameters to be modified and the objective function,and finally the optimized modified parameters were obtained.The results of engineering example show that the accuracy of the modified finite element model is improved to a certain extent,and the accuracy error between the modified finite element model and the measured data can be guaranteed within 5%,which can be used as a benchmark model for the risk assessment of foundation pit deformation.