Prediction And Control Of Adjacent Buildings’ Settlement Caused By Shield Tunnel Construction In Nanning

With the wide application of shield method in metro construction,more and more attention is paid to the influence of shield tunnel construction on the buildings surface settlement.Therefore,it is very important to accurately predict the buildings subsidence,and take effective control measures in the design and construction,so as to prevent the occurrence of accidents.Because of the application of shield method is the first time in Nanning area,so at present,the research on the application of shield construction in Nanning is still less.Therefore,it is necessary to conduct in-depth study.In this paper,through statistical analysis and numerical calculation model of the monitoring data,variation of the variation in the influence of different geological conditions and different type of foundation settlement of shield in the process of surface buildings,buildings,analysis results show that:(1)According to the Peck empirical formula,the width coefficient of the settlement trough and the rate of the loss of the formation are all:silt layer>gravel stratum>mudstone and silty mudstone stratum.By finite element analysis,the variation of the width of the settlement trough of the settlement curve of the building is consistent with the ground settlement law.However,under the same formation condition,the settling tank is more flat,and the formation loss rate is smaller than that of the surface.(2)The settlement of shield tunnel passing through different foundation buildings,the calculated values are close to the monitoring data,The combination of the pile foundation and the underlying soil layer is good,and the settlement value and the maximum inclination are about 50%for shallow foundation.The influence of shield on the deep foundation is also reflected in the lateral deformation of the pile,and the maximum deformation occurs in the middle of the first row of’piles near the tunnel.Pile farther away from the tunnel,smaller deformation.Based on the project of Baicang ridge～Train station in Nanning Metro Line 1,according to the characteristics of the building settlement curve caused by shield tunnel construction,and based on the factors such as the depth of the foundation,the stiffness and the relative position of the tunnel under different geological conditions,the settlement parameters of the Peck formula of surface subsidence are modified to get the prediction formula of the building settlement.And the range of buildings as an example,the prediction of the building settlement calculation formula were compared with the actual measured values,the calculated values close to the monitoring value prediction fitting correlation coefficient is 82%,the error rate of around 15%,the results show that the prediction method has certain accuracy.The variation of the measured settlement data and shield construction parameters based on the analysis of the relations of construction parameters and surface settlement value analysis,building the grey relational analysis,the construction parameters of ground settlement and settlement on the sensitivity from big to small in order:driving speed,grouting quantity,air cushion pressure,cutter head torque,thrust,excavation chamber pressure.The sensitivity of buildings subsidence from large to small is as follows:grouting quantity,driving speed,thrust,air cushion pressure,digging chamber pressure.According to the settlement control standard comparison site monitoring data with the existing surface and building,that geological conditions in the third(Full cross section of silty sand through the silt stratum)or fifth(The upper part of the lower mudstone siltstone layer and upper lower mudstone gravel layer)class building settlement is relatively large,some measured value exceeds the control value.In addition to the whole section through the gravel layer subsidence rate of the larger,to control the adverse disaster.Therefore,based on the experience of setting parameters of shield construction,the paper puts forward the suggestion of the construction parameters of shield tunnel using the slurry pressure balance shield tunneling method through the two kinds of geological conditions.