| In recent years,with the rapid growth of China's economy,the domestic urban rail transit construction has developed rapidly,and subway shield tunnel projects have also increased.However,in the face of so many engineering construction projects,we will have to solve all kinds of complicated engineering problems.Among them,the ground settlement caused by the tunneling of shield tunnels is one of the important problems in subway construction.Excessive ground settlement will adversely affect neighboring buildings and even threaten the safety of life and property.Although scholars at home and abroad have done a lot of research on the influence of shield tunneling construction on adjacent buildings,the influence of shield tunnel construction on the surrounding soil is affected by factors such as shield machine type,tunnel burial depth and stratum conditions.The impacts are different and have certain pertinence,especially for the research of shield tunnels in red sandstone strata crossing adjacent buildings is still insufficient.Therefore,in this paper,using the shield tunnel section of the Lanzhou red sandstone stratum as the engineering background,the ground subsidence control standards are formulated.Applying the modified Sagaseta formula to theoretical analysis of the ground surface longitudinal settlement induced by shield tunneling,At the same time,with the help of the geotechnical finite element software MIDAS/GTS,the numerical analysis of the shield tunnel passing through adjacent high-rise buildings and masonry structures is carried out.The research conclusions provide a reference and basis for the construction of subways under similar ground in cities.This paper takes the Lanzhou red sandstone stratum subway shield tunnel crossing adjacent high-rise buildings and masonry structures as the engineering background,and uses the analytical analysis of the modified Sagaseta formula theoretical analysis and numerical method MIDAS/GTS software to carry out simulation analysis.The following results are obtained:(1)Based on the mechanical mechanism and characteristics of shield tunnel construction,this paper analyzes the disturbance of shield tunneling to surrounding strata and the influence factors on different neighboring buildings,and clarifies the general law of stratum deformation.Based on the control of the tilting deformation of the building foundation and the control of the bending deformation of the building foundation as two important control indicators,the ground settlement control standard was obtained,that is,the allowable settlement of the high-rise building surface is 30 mm,and the allowable settlement of the masonry structure surface is 25mm;(2)The Sagaseta formula considering the influence of excavation face balance,shield tail gap,shield tail grouting and other factors can better reflect the distribution law of vertical surface settlement;(3)The maximum settlement of the key control points caused by the shield passing through high-rise buildings is 13.6mm,which is less than the control standard;the maximum settlement of the key control points caused by passing through the masonry structure is 28.33 mm,which is greater than the control standard,and protective measures should be taken;(4)By comprehensively considering factors such as the spatial position relationship between the double-line tunnel and the building,the size of the ground displacement and settlement exceeding the control standard,and economic indicators,the grouting reinforcement measures were adopted to ensure the safe construction of the shield tunnel.The analysis shows that the distribution of the overall surface settlement law is basically unchanged after reinforcement,but the surface settlement amount at each location is significantly reduced,the settlement groove is significantly shallower,and the surface settlement at the maximum settlement point h is reduced by 29.33%,and the settlement amount is 20.02 mm.Adopt grouting reinforcement to meet engineering requirements. |
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