基于PSO-RF-NSGA-Ⅱ盾构下穿施工既有隧道变形预测与优化控制

Prediction and Optimization Control of Deformation of Existing Tunnel Induced by Undercrossing of Shield Tunnel Based on Particle Swarm Optimization-Random Forest-Nondominated Sorting Genetic AlgorithmⅡ

盾构施工引起的土体扰动与既有隧道承载力的相互作用会造成竖向和横向变形,给既有隧道的正常运行带来潜在风险。为精准预测并有效控制盾构下穿施工既有隧道变形,构建粒子群优化(particle swarm optimization,PSO)、随机森林(random forest,RF)及带精英策略的非支配排序遗传算法(non-dominated sorting genetic algorithmⅡ,NSGA-Ⅱ)多目标优化框架。基于监测的样本数据集,采用PSO-RF模型对既有隧道拱底位移进行预测,得到盾构隧道主要施工参数与拱底位移的非线性映射关系;基于构建的PSO-RF-NSGA-Ⅱ多目标优化框架,对拱底竖向位移和拱底横向位移2个目标进行优化,获得盾构施工参数的帕累托(Pareto)前沿;采用TOPSIS方法计算得到最优解,实现盾构下穿施工既有隧道变形的精准预测。结果表明,采用基于PSO-RF-NSGA-Ⅱ框架的盾构施工参数组合进行优化控制,既有隧道的拱底竖向位移和拱底横向位移分别降低了33.6%和35.1%,实现了盾构下穿施工既有隧道变形的精确预测与控制。

The soil disturbance induced by a shield tunnel can affect the bearing capacity of the existing tunnel,and the resulting vertical and horizontal deformation of the existing tunnel poses risks to normal operation.To accurately predict and effectively control the deformation of the existing tunnel induced by the undercrossing of the shield tunnel,a multiobjective optimization framework is constructed that integrates particle swarm optimization(PSO),random forest(RF),and non-dominated sorting genetic algorithmⅡ(NSGA-Ⅱ).A monitored sample data set is used in conjunction with the PSO-RF model to predict the displacement at the tunnel bottom,whereby a nonlinear mapping relationship between the main construction parameters of the shield tunnel and the bottom displacement is obtained.The constructed PSO-RF-NSGA-Ⅱmultiobjective optimization framework is used to optimize the bottom settlement and horizontal displacement of the existing tunnel,yielding the Pareto front of the shield tunneling parameters.The TOPSIS method is used to calculate the optimal solution to accurately predict the deformation of the existing tunnel.Optimization and control using PSO-RF-NSGA-Ⅱwere found to reduce the bottom settlement and horizontal displacement of the existing tunnel by 33.6%and 35.1%,respectively,thus realizing accurate prediction and control of the deformation of the existing tunnel induced by undercrossing of a shield tunnel.