Study On The Law Of Soil Settlement Caused By Shield Tunneling In Sandy Clay Composite Stratum

In order to meet the growing urban population,urban construction will inevitably need to be correspondingly rapid development in order to adapt to it.As a result,the area of land available for urban use is decreasing,the urban area is expanding,and ground transportation is becoming more and more overwhelmed.People have difficulty commuting.As one of the primary construction methods of subway tunnels,shield has the advantages of small disturbance to the soil and is widely used in underground engineering construction at home and abroad.However,the construction of the shield will still cause some disturbance to the soil around the tunnel,causing the displacement of the ground and the surface settlement to affect the surrounding environment,which in turn affects the buildings around the tunnel.As far as the sand-adhesive composite soil layer is concerned,the gravel soil has a loose structure with no cementation,a cohesive force close to zero and a large friction angle,and is a soil body with poor self-stability.In the shield construction of sand-bonded composite soil layer,it is prone to problems such as collapse of sand layer,actual tunneling route of shield machine and deviation of planned route,and even lead to large-scale surface settlement,which is the surrounding of shield construction and construction site.Buildings pose great security risks.Based on the shield tunnel construction project of a certain section of Guangzhou Metro,this paper studies the lateral settlement deformation of six monitoring sections in sand-bonded composite stratum,and uses finite element software to simulate the construction stage of shield under four different stratum conditions.The work and conclusions are as follows:(1)Using three classical surface settlement prediction formulas to predict and compare the surface subsidence of sand-bonded composite formations,the results show that the sand-bonded composite formation is suitable for settlement prediction using Peck calculation formula and Attewell calculation formula.Sagaseta calculation formula is not suitable.Sand-bonded composite formations are used.The Gaussian peak function is used to monitor the lateral settlement deformation of the section to fit the fitting,and the fitting value of the subsidence width coefficient i is obtained.The deviation of the settlement tank is analyzed by the Gaussian peak function fitting curve.The result shows that the sand-adhesive composite settlement is set.There is no obvious law of groove offset;the weighted correction formula of the settlement coefficient of the settlement of the composite formation is proposed and the correction result is compared with the fitting result,which shows the reliability of the correction formula.(2)Using MIDAS GTS NX finite element software to simulate the shield construction process under four different formation conditions,summarizing the key stages of settlement formation under sand-bonded composite formation conditions and the settlement ratio of each stage;The stratified settlement analysis is carried out,and the variation of settlement width and axis settlement with soil depth is given.The time history curve of surface settlement is analyzed,and the position and specific change of the time-history curve of surface subsidence of sand-bonded composite formation are given.law.(3)Compare the fitting value of the monitoring data and the numerical simulation value with the lateral settlement value of the measured surface,and compare the simulation value and the measured value of the surface settlement time curve,it is feasible to use the fitting function and numerical analysis method.