Research On The Influence Of Shield Tunneling Parameters On Ground Settlement And Deformation

At present,the mileage of metro lines operating in China is increasing year by year and many problems have been encountered during the construction of the metro.Based on Nantong Railway Line 1,the paper summarises and analyses the evolution of shield excavation parameters on ground deformation through statistical analysis of literature,theoretical research,field measurements,numerical simulation and neural networks,and explores in depth the spatial and temporal characteristics of ground settlement and adjacent buildings caused by the shield excavation process,and constructs a ground settlement prediction model based on BP neural networks.The main research contents are as follows:(1)Firstly,the interaction mechanism between shield excavation and ground deformation characteristics in the Nantong area was analysed based on field measurement data,and the basic laws of ground surface and adjacent building deformation caused by the shield excavation process were obtained.It was found that the cumulative peak ground settlement and the peak settlement and tilt of the adjacent buildings caused by the shield tunnel excavation in the three lines of tunnels did not exceed the control standard.This indicates that controlling the propulsion speed,ensuring the balance of the working face and maintaining the stability of the shield can effectively reduce the surface settlement during the shield excavation process.(2)Then the tunneling parameters of the shield machine were analyzed in two aspects: optimization of tunneling parameters and the degree of influence of different changes of tunneling parameters on the ground settlement through the study section.It is found that the correlation between the tunneling parameters is not very strong;the degree of influence on the surface settlement is in the following order: cutter torque >total thrust > soil pressure > propulsion speed > grouting volume > grouting pressure > soil discharge volume > cutter speed.(3)Then,based on ABAQUS+FLAC3D large numerical simulation software,a numerical simulation of the whole process of shield tunnel boring through dense building complexes in small spaced three-line tunnels was carried out to establish a mechanical analysis model of shield machine-ground-building(structure)foundation working together to analyze the lateral settlement,longitudinal settlement,settlement and tilt law of adjacent buildings.(4)Finally,an intelligent prediction method for shield-disturbing ground settlement under super-deep water-rich sand formation conditions is proposed based on the on-site settlement monitoring data,and the model parameters are continuously optimized to finally obtain an intelligent prediction model for the ground settlement induced by the shield tunneling process of undercutting dense buildings under super-deep water-rich sand formation conditions.