Research On Surrounding Rock And Surface Deformation Law Which Is Induced By Building Construction Of Underground Excavated Loess Subway Tunnel

In the loess area,the research on deformation rule of surface and surrounding rock which is induced by building construction of shallow tunnel under the subway tunnel has important value.In this paper,based on xi 'an metro 4 line of tunnel,the shallow tunnel project,Theoretical analysis,numerical simulation and field monitoring were used to do research work.The main conclusions are as follows:(1)The influence factors of the surface and building deformation of tunnel in loess by mine construction under buildings was studied and mainly include:Engineering geological condition?dimension of excavation section?the distance between buildings and the center line of the tunnel.The main factors that analyzed the deformation of surrounding rock of loess subway tunnel include:Physical and mechanical characteristics of loess in a tunnel?tunnel buried depth?the basic types of structures?the excavation method of tunnel?Formation loss?Construction organization management.The deformation mechanism of formation is analyzed.(2)Based on a tunnel in Xi'an Metro Line 4,using FLAC3D software is used to establish three-dimensional calculation model of loess tunnel under existing buildings,The deformation laws of surrounding rock and the surface induced by three construction methods such as CD method,CRD method and step method are simulated and predicted.The results shows:the effect of the CRD construction method,used in the control of surrounding rock and ground surface deformation and building deformation,is best,CD can take second place and step method which set aside core induced the largest deformation of surface and building.The suggestion that the CRD method was adopted to improve the construction of running tunnel under buildings is put forward.(3)The analysis of FLAC shows:the vertical settlement of building was affected by construction of tunnel under adjacent buildings,but the differential settlement of the structure was small,the deformation of the structure was small when the construction of tunnel lateral through the buildings,but the differential settlement of building is larger and the building was prone to appear uneven settlement.The deformation law of surrounding rock caused by subsurface excavation of buried subway tunnel under existing building has undergone three stages:slow growth,rapid deformation and basic stability.The stratum reinforcement measures of underground subway tunnel were proposed and was analyzed by FLAC,which suggests that CRD method in the reinforcement measures that is put forward can ensure the safety of the tunnel under wear existing buildings.(4)The precipitation scheme,the ground surface and the settlement deformation monitoring plan of the tunnel are formulated.Practice shows that deformation of surrounding rock and the ground surface and building settlement are under control after construction of concealed excavation of tunnels in CRD methods that is proposed.Monitoring value and FLAC forecast is basically match.