Analysis of deformation patterns of ground surface and existing tunnels caused by overlapping tunnels
To study the surface settlement and tunnel deformation caused by the new shield tunnel passing through the existing tunnel,the construction of Wuhan Metro Line 5 Phase Ⅰ project was taken as the back-ground.The FLAC3D software was used for numerical simulation to analyze the influence of the construc-tion of the new left-line tunnel on the deformation of the underlying left-line and the overpass right-line tunnels and the surface soil,and the results were compared with the field measurement results.The results show that the new overpass tunnel has little effect on the horizontal deformation of the existing tunnel,and it is necessary to focus on the vertical deformation of the existing tunnel and the deformation monitoring of the shield area;as the new tunnel face advances,the deformation rate of the existing tunnel increases as it is closer to the face;the surface settlement outside the tunnel caused by excavation conforms to the normal excavation settlement law,i.e.,the closer to the center of the tunnel,the greater the surface settlement,the faster the surface deformation rate is when excavating is close to the middle,and the slower the deformation rate is when excavating is close to the stable stage;finally,compared with the actual project,it is found that the maximum error between the numerical simulation results of the surface settlement after the overlapping section excavation is completed and the surface monitoring data of the actual shield construction site is only 4.32 mm,which is within the error range.The research results have certain guiding value for engineering applications and can provide reference for projects under similar working conditions.
shield tunneling cross over the existing tunneldeformation featuresurface settlementnumeri-cal simulationfield monitoring