Research On The Existing Tunnel Deformation Influenced By The Construction Of Opened-excavated Tunnel And The Reinforcement Measures

With the continuous expansion of the scale of urban development, the development and utilization of underground space has entered a new stage of heat. However, more and more technical problems appeared in the development process, for example, as the distance between the tunnel and the other structures becomes much closer, a sharp increase in the difficulty of construction. The unloading engineering construction of the open cut tunnel is close to the existing tunnel because of the excavation of the upper tunnel, the influence of the construction process on the existing subway tunnel needs us to explore and judge. It is precisely because of the necessity of the research on the law of settlement and deformation of existing metro tunnels. In this paper, combined with an domestic open cut box type foundation pit in the tunnel crossing existing subway tunnel, adopt the means of theoretical analysis, numerical simulation and from the excavation construction methods, reinforcement scheme and the existing subway tunnel control deformation, to ensure the safety of the tunnel construction and the normal operation of the measures, the following works have been carried out in this thesis:(1)The simplified calculation formula of "Mindlin solution" and "chain rod method" is used to calculate the longitudinal displacement of tunnel structure, the method can be used to evaluate the influence of foundation pit construction on the longitudinal displacement and internal force of the adjacent tunnel relatively quickly at the initial stage. And the calculation results of the method are compared with the measured results of the existing cases.(2) According to the working conditions of the excavation process of the existing tunnel, three possible excavation schemes are discussed, and the results are analyzed.(3) Compared with the bench method and pipe curtain method, bench method reinforcement construction is simple, the environmental impact of the foundation pit is small, and the surrounding environment of the foundation pit is low, and the cost of the effect is better than that of the pipe curtain method.(4) Only consider the under floor reinforcement effect, the existing beneath subway tunnel uplift displacement in the foundation pit and below both the subway tunnel plane projection center cross position to reach the maximum, considering the uplift scale is still great, it is needed to uplift pile construction combined with the pile reinforcement design.(5)The effect of anti-uplift pile spacing on the reinforcement effect was analyzed according to the bench method. Anti-uplift pile spacing to reduce the impact of the reinforcement effect is limited, considering the cost, it should be reasonable to set the anti uplift pile reinforcement spacing.The results could be referred to design,construcyion and maintenance of related project.