Finite Element Analysis And Automatic Monitoring Of Structural Deformation In Metro Shield Tunneling Underneath High-speed Railway Tunnel

With the rapid expansion of cities,urban subway has become one of the main means of urban transportation,and is rapidly building in large and medium-sized cities.Shield tunneling is nowadays the important excavation method of urban subway which has the advantages of fast speed,no impact on ground traffic,high precision and so on.The subway shield construction will often penetrate existing structures on the ground,which leads to the lack of underground rock layers of the structures,resulting in the redistribution of the internal forces of the structures adjacent to the subway shield construction,resulting in uncoordinated and uneven deformation,resulting in the structures and underground deformation and even structural damage of rock layers and soils induces hidden safety hazards and accidents of structures and underground rock layers and soils.This study takes Changsha metro line 3 down-traversing Liuyang river tunnel project as an example,uses MIDAS/GTS NX wear high-speed under the subway shield tunnel structure deformation finite element analysis,and uses TM50 measuring robot automation for deformation monitoring and early warning for the project,finally compares the finite element calculation results to the measured results.Main research contents and achievements are as follows:(1)The thesis uses the Midas/GTS NX finite element software to establish a three-dimensional finite element calculation model based on the spatial position relationship between the shield tunnel and the Liuyang river tunnel of the Beijing-Guangzhou railway to simulate and analyze the influence of the shield underpass construction on the strata at different depths and the existing high-speed railway tunnel.The results show that the existence of existing high-speed railway tunnel changes the displacement field,objectively retarding the movement of the displacement field and slowing down the deformation of the stratum above the tunnel.When the crossing of the right line is completed,the overall maximum settlement point of the existing tunnel appears at the crossing point of the existing tunnel arch bottom,forming a settlement groove centered on the crossing point with the maximum settlement value of 1.4mm.In the stage when the cutter head of the shield tunneling machine reaches the outer side line of the existing high-speed railway tunnel and the tail of the shield completely leaves the existing high-speed railway tunnel,the settlement amount is the largest,accounting for 92.2%of the total settlement.Using MIDAS/GTS NX to conduct finite element analysis of structural deformation of subway shield tunnel through high-speed railway has certain guiding significance for automatic monitoring.(2)The thesis uses the measuring robot TM50 and the GeoMoS monitoring system to collect the original deformation data of existing high-speed railway tunnel.The data processing and integration were carried out by combining the method of difference and Kalman filter processing method to collect the real data reflecting the structural deformation of existing high-speed railway tunnel.The automatic monitoring data of right line shield tunneling is analyzed emphatically,and the influence law of shield tunneling on existing high-speed railway tunnel is summarized.The analysis results show that with the continuous advance of right line shield,the overall settlement curve of the tunnel shows a v-shaped trend,forming a settlement groove centered on the crossing point.In the process of crossing,the maximum settlement point appears directly above the right line shield tunnel,and the maximum settlement value is 0.8mm.With the continuous tunneling of shield tunneling,the settlement groove gradually becomes deeper and narrower.After the tail of the shield detached from the monitoring section,due to the increasing settlement,the secondary grouting and multiple grouting were carried out,which caused the settlement tank to shift to the right,and the maximum settlement value was controlled at 0.9mm.(3)The thesis uses finite element analysis data and automatic monitoring data for comparative analysis.The results show that the two trends are consistent in the process of shield tunneling.The finite element model can theoretically analyze and predict the deformation of the existing tunnel from the perspective of structure and mechanics,while the reliability of the finite element model can be verified from the perspective of deformation results by automatic monitoring.And after completion of the cross,both curve appeared a greater degree of deviation.The reason is that shield tail after completely from the monitoring section,according to the quality of shield through the feedback in the process of automatic monitoring data of shield thrust,soil bin real-time adjusting parameters such as pressure and grouting quantity and secondary grouting,the deviation in the theoretical value and practical value.Thus,the finite element model can be used for theoretical calculation and prediction of structural deformation in the construction process,and the automatic monitoring can monitor and truly reflect the actual deformation value and deformation trend of existing tunnels.