Research On The Influence And Deformation Control Technology Of Collinear Shield Tunnel By Approaching Construction Of Long-distance Comprehensive Pipe Gallery Foundation Pit

With the development of urban construction concept,a number of urban rail transit and comprehensive pipe gallery co-construction projects have emerged.At present,there is little research on corridor-rail co-construction projects,and the construction of comprehensive pipe gallery foundation pit and interval subway tunnel with long distance and small clear spacing makes the engineering environment more complicated.Based on the simultaneous co-construction project of Shenzhen Metro Line 12 comprehensive pipe gallery and subway,this paper systematically studied the mutual influence law of the two constructions through literature review,numerical simulation,multi-objective optimization,on-site monitoring and other methods.The main research contents and conclusions are as follows:(1)Research on the mutual influence law between subway tunnel tunnel group and comprehensive pipe gallery in different spatial locations and construction sequence: in order to minimize the mutual influence between the two,priority should be given to the tunneling of subway tunnel in each construction interval before the excavation of pipe gallery foundation pit.(2)From the perspective of tunnel confining pressure changes caused by foundation pit excavation,research on the change rules of tunnel displacement and internal force during shield tunnel excavation after comprehensive pipe gallery excavation: the unloading of soil during foundation pit excavation causes the confining pressure difference between the underlying tunnel and the adjacent tunnel,which moves towards the side with the larger confining pressure reduction.With the decrease of the thickness of the interlayer soil and the increase of the excavation length and depth,the displacement and internal force reduction of the double-track tunnel gradually increase.(3)Research on the influence of the depth of bored piles embedded in the foundation pit of the comprehensive pipe gallery,the grouting range of the interlayer soil,the different excavation methods and the pile load pressure in the tunnel on the shield tunnel in the interval: the construction of the foundation pit of the comprehensive pipe gallery using the separate spacing method can effectively reduce the displacement of the underlying tunnel;there is an optimal depth of bored piles and the thickness of the grouting reinforcement layer to minimize the displacement of the tunnel;the stacking load in the tunnel can effectively inhibit the floating of the underlying tunnel,but the excessive large ballast will greatly increase its convergence deformation.(4)Further considering the cooperative optimization of tunnel deformation control and construction cost,six parameter variables were introduced to build the PSO-LSSVM tunnel displacement prediction model,and the Pareto optimal solution set was obtained by invoking the fitness function of PSO-LSSVM through NSGA-II genetic algorithm.According to the actual engineering needs,the optimal construction scheme was obtained.(5)Based on the analysis of the measured data of subway tunnel,the displacement law of tunnel under the separate spacing excavation of long distance comprehensive tunnel foundation pit is summarized,and the reliability of numerical model and multiobjective optimization model is verified by comparing the simulated value with the measured value.