Optimization analysis of supporting parameters of small-diameter pipe roof-beam in metro station

YANG Xuhui; BAI Qian; JIA Pengjiao

doi:10.7688/j.issn.1000-1646.2025.01.15

Abstract：[Objective]The pipe roof method can significantly reduce the ground disturbance caused by excavation and is widely used in underground space construction.However,the current pipe roof method has the problems of complicated connection between pipes and long construction period.A novel pipe roof support system was put forward to solve the above problems.[Methods]Firstly,the fine model of the station constructed by the small-diameter pipe roof-beam method was established by using FLAC3D software,and the influence of the support parameters such as pipe roof spacing,pipe roof stiffness,number of beams,and beam stiffness on surface settlement and pipe roof deformation was investigated,which was followed by optimization analyses of the key parameters.Finally,the numerical model was verified by field monitoring data,and it was compared with the results of similar stations using other construction methods.[Results]The effects of the number of beams on surface settlement and pipe roof deformation are highly significant.With the increase in the number of beams,the maximum values of surface settlement and pipe roof deformation generally show a quadratic decreasing trend.The increase in pipe roof spacing does not have a significant effect on surface settlement and pipe roof deformation.Pipe roof stiffness has a great impact on the maximum values of surface settlement and pipe roof deformation.With the pipe roof stiffness of 2K,the bearing capacity of the pipe roof has been fully utilized,and bending stiffness is no longer a key factor in controlling the deformation.When the beam stiffness is in the range of 0.5D-3D,the maximum values of surface settlement and pipe roof deformation are quadratic with the beam stiffness.When the beam stiffness is increased from 2D to 3D,the change of the maximum values of surface settlement and pipe roof deformation is not obvious,and the decrease is within 3％.This indicates that when the beam stiffness is 2D,the flexural performance of the beam has been fully applied,and continuing to increase the flexural stiffness will not have a significant impact on the deformation values,but will cause a waste of engineering materials.[Conclusion]Under the condition of given control standard,the combination of parameters of small-diameter pipe roof-beam can be selected according to the actual demand and site conditions during construction,and this paper gives the reasonable matching relationship between parameters of small-diameter pipe roof-beam when the surface settlement control standard is 30 mm.Compared with the construction methods for similar metro stations,the small-diameter pipe roof-beam method greatly shortens the construction period while meeting the surface settlement control standards,which is worthy of further promotion and application.The innovation of this paper is to propose a novel pipe roof support system for the construction of metro stations and to optimize the key parameters of this support system,which can provide reference for the current underground space construction.