| The national "14th five year plan" puts forward the development requirements of "accelerating the construction of a transportation power and orderly promoting the development of urban rail transit".As an important system of urban rail transit,Metro is the lifeline of major infrastructure projects of urban transport.By December 2021,48 cities in mainland China have opened subway lines,with a total operating mileage of 7253.73 kilometers.It is estimated that the operating mileage of urban rail transit in China will reach 13700 kilometers by 2026.Subway tunnels inevitably cross water rich strata.Affected by the corrosive environment,extreme conditions,disasters,collisions and other factors,as well as the assembly control accuracy and synchronous grouting quality,segment structures as shield tunnel barriers often have structural cracking,dislocation,damage and other problems,which will cause the deformation of surrounding strata,and seriously cause surface collapse and building overturning,seriously endangering the engineering safety and the safety of people’s lives and property.Based on Jinan Rail Transit Line 2 project,through indoor experiments and numerical simulation research methods,this thesis studies the optimal ratio of synchronous grouting slurry,reveals the stress characteristics of synchronous grouting segments and the law of surface deformation,and puts forward control measures to control surface settlement in combination with on-site surface settlement monitoring data.The main research work and results are as follows:（1）The indoor experimental study on the proportioning of synchronous grouting slurry was carried out,and the influence laws of water cement ratio,fly ash content,slag soil ratio,quicklime content and expansive agent content on slurry consistency,stone rate,bleeding rate,setting time,fluidity and compressive strength were analyzed respectively.The influence laws of single factor on the strength of synchronous grouting materials were revealed,and the optimal proportioning of synchronous grouting slurry was proposed.The 28 d compressive strength was2.12 MPa,which met the construction requirements.（2）Taking the Feng-Peng section of Jinan Metro Line 2 as the prototype,using ABAQUS simulation software,a numerical simulation model for the whole process of shield tunneling is built.Considering the synchronous grouting slurry parameters and grouting parameters,the surface settlement and segment stress analysis of shield tunneling are carried out.The following conclusions are obtained: the shield construction causes shear damage to the stratum,and stress concentration occurs at the excavation surface,The influence of shield construction on the surface lateral settlement is within 20 m（3D）from the tunnel axis;With the increase of soil depth,the width coefficient of lateral settlement trough decreases gradually,and the width of settlement trough decreases;With the advance of the shield,the top segment sinks,the bottom segment floats,the left and right segments displace away from the tunnel axis,and the maximum horizontal surface settlement shows a trend of deceleration and increase;The axial surface settlement is "s" shaped,and the maximum axial surface settlement increases with the advance of the shield.（3）In order to further study the influence of synchronous grouting construction on segment stress and surface settlement,the influence laws of four factors,namely,grouting amount,grouting pressure,elastic modulus of grouting materials and Poisson’s ratio,are analyzed respectively.The results show that the adjustment of grouting amount,grouting pressure,elastic modulus of grouting materials and Poisson’s ratio has little effect on the overall change law of surface transverse and axial settlement and segment displacement;The horizontal surface subsidence is symmetrical "groove" shape,and the axial surface subsidence along the advancing direction has little difference;The increase of grouting parameters can effectively control the horizontal and axial surface settlement and the top segment settlement;The bottom segment floats up and the right segment displacement increases with the increase of grouting parameters;The grouting pressure should be between 0.45-0.55 MPa,the elastic modulus of the grouting material should be between 300-400 MPa,and the Poisson’s ratio should not be greater than 0.3.（4）The field monitoring data of surface subsidence are compared with the numerical calculation results,and it is found that the two are in good agreement,which verifies the accuracy of the numerical calculation.The control measures of surface subsidence are put forward. |
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