Study Of Soil Deformation And Stability In The Process Of Shield Metro Tunnel Excavation Under Sandy Silt Strata

In the subway tunnel excavation at present, shield method is adoptedmore and more widely, yet in the process of the excavation in sandy silt,there is always significant settlement which is difficult to be controlled atthe ground on top of the tunnel. So, how to ensure the grounddisplacement in a reasonable range in construction and ensure normal useof the upper structures and underground pipelines nearby become arealistic issue to be solved, it is necessary to research the grounddeformation and stability in the process of shield construction, which is ofremarkable practical value.In this paper the predecessors’ research was analysed，by which themechanism of ground settlement, the factors on ground settlement and itsdistribution characteristics was concluded. Based on the construction ofshield metro tunnel of the section the bus station to the century roadstation of The No.1Line of the Hangzhou Subway，bid section Ⅲ, the3D model was created using MSC.PATRAN and introduced into thesoftware FLAC^3D of three-dimensional fast lagrangian analysis ofcontinua method. By simulation on shaft and tunnel excavation, the stressand displacement distribution of diaphragm wall, soil displacementaround shaft at active earth pressure, ground traverse and longitudinalsettlement trough variation in the course of tunnel excavation, stress distribution and space convergence on liner etc is researched. With thecomparison between the numerical simulation and in-situ monitoringresult, reasonableness of the former method was identified. Also, with theground settlement comparison at different excavation path to twin-tracktunnel, the effects excavation path on settlement was obtained. Finally,ground settlement numerical simulation results considering stratum waterloss was researched and was compared to the situation that withoutconsidering water loss, the influence of seepage factor to groundsettlement was obtained.