| In recent years,China’s Urban Rail Transit Industry has developed rapidly.By the end of2017,33 cities in China were operating urban rail transit,with a total mileage of 4712 km.The total mileage of Metro Line is 3884 km,accounting for 82.4% of the total mileage of Rail Transit.Because of the complexity of urban building environment,eg.the density of buildings and the complexity of underground pipelines,shield construction is a common construction method in urban subway construction to reduce the impact on urban life.The influence of shield construction on ground deformation is caused by many factors,including driving speed,face thrust,grouting pressure,cutter head torque,soil parameters and so on.In this paper,the orthogonal test under multi-factors is designed,and the range analysis of FLAC3 D numerical calculation results shows that the grouting pressure is the most important factor to the ground deformation during the shield construction.Then,the influence of the uncertainty of grouting pressure on the deformation of stratum after shield excavation is analyzed,and the feasibility of the simulation method is verified by comparing with the results in literatures.Then,in this paper,the parameters needed for numerical analysis are back-analyzed based on Genetic Algorithm combined with on-site monitoring data.In this process,by virtue of the superiority of Neural Network in establishing highly nonlinear model,the mapping model between construction parameters and surface displacement is established to replace the numerical simulation calculation process of the forward analysis process so as to reduce the calculation workload of the forward numerical simulation.Finally,numerical simulation is carried out again based on the parameters obtained from back analysis,and the influence of the more accurate shield construction on the additional response of adjacent loaded piles is analyzed.The main research results are as follows:(1)by completing the ORTHOGONAL experiment,based on FLAC3 D numerical simulation method,the influence of grouting pressure,push force,compression modulus and undrained shear strength on ground deformation is analyzed and studied in this paper.The results show that grouting pressure has a greater influence on the formation deformation than other factors.(2)firstly,the mapping model of grouting pressure-surface settlement is established,then the grouting pressure back analysis is carried out,and a complete "precise simulation algorithm based on displacement back analysis principle" is constructed,based on the monitoring data of finite points,the additional response values of adjacent loaded piles in each construction stage can be inversed.(3)during the construction of shield tunnel,the uncertainty of construction parameters has obvious influence on the additional response of adjacent pile foundation,especially on the additional bending moment of pile. |
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