| With the rapid development of economic globalization in the past decade,the process of urban-rural integration has gradually accelerated,and urban underground rail transit is also facing a test while growing rapidly.Among the many methods of subway tunnel construction,the shield method has been applied in many practical projects due to its high safety and fast construction rate,and has become one of the common methods for construction of subway tunnels at home and abroad.However,during the tunnel excavation process using the shield method,the soil and buildings in the vicinity of the project area will be disturbed,resulting in settlement on the surface.How to reduce the surface subsidence caused by tunnel excavation is also a problem that needs to be solved in actual engineering construction.Therefore,it is meaningful to study the ground settlement law and influencing factors caused by tunnel shield excavation.Based on the related articles on a large number of tunnels at home and abroad,this paper takes the construction of subway tunnel from Shenzhou Road Station to Science Square Station as the engineering background.Based on the hydrogeological conditions of the actual project,the numerical analysis model of 3D double-track tunnel is established and adopted.The method of finite element numerical simulation is carried out,the corresponding calculation and analysis are carried out,the statistical calculation results are compared,and the actual monitoring results of the background engineering part are compared and analyzed to verify the accuracy of the model and analyze the horizontal and vertical settlement laws of the tunnel surface;Then,according to the principle of single variable,the effects of various factors such as tunneling pressure,tunnel depth,grouting conditions,excavation size and construction excavation mode on the surface subsidence change are simulated.Finally,the empirical formula and numerical simulation pair are combined.The law of lateral settlement curve of the ground shield tunnel is analyzed,which provides the basis for calculation and analysis for the construction of related projects.The main research results are as follows:(1)When the shield tunnel is subjected to single-track excavation,the horizontal settlement curve of the ground surface is continuously deepened and widened with the excavation of the tunnel.The maximum settlement occurs on the centerline of the tunnel;when the shield tunnel is double-tracked At the centerline of the shield tunnel,the surface settlement is superimposed,and the lateral settlement curve of the surface gradually moves toward the centerline of the double-line tunnel as the tunnel is excavated.(2)In the case of geological conditions,construction methods and other factors,when tunnel construction is excavated,the shield tunneling pressure can be increased to a certain extent to reduce the lateral lateral settlement;the soil caused by tunnel construction excavation The amount of settlement decreases as the thickness of the buried depth increases.(3)In the construction process of the double-line shield tunnel,when the tunnel shield tail grouting is carried out,when the elastic modulus of the grouting layer increases,the ground surface settlement caused by the tunnel is continuously reduced,and the actual project can be appropriately increased.The elastic modulus of the slurry layer improves the stability of the soil and reduces the surface settlement.When the tunneling size increases,the maximum lateral settlement of the ground surface also increases gradually.The construction excavation mode of the shield tunnel has less impact on the surface settlement.(4)The form of surface settlement curve of double-line shield tunnel has a certain relationship with the axial distance of the tunnel.As the axial distance of the double-line tunnel increases,the form of the surface settlement curve of the tunnel slowly changes from the "V" shape to the "W" form.Changes,while the surface settlement gradually decreases. |
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