Research On Mechanism And The Parameters Of Pipe Roof Reinforcement Of Double-arch Tunnels Under Unsymmetrical Pressure

In order to reduce the impact on ground activities and other underground facilities and pipelines,Pipe shed method as a method belong to shallow buried excavation method has recently got widely used in tunnel and underground engineering.Pipe roof is an assisted method used for tunnel construction,it mainly provides temporary retaining facilities for tunnel excavation.at the same time,reduce the impact of in the process of construction on the ground and other underground facilities and pipelines.Pipe shed method has the advantage that can't be replaced by other method.especially in tunnel construction of overburden thickness smaller but not apply to cut and cover method construction engineering.This paper basis on familiar with the characteristic of pipe shed method of construction,Comprehensive utilization theory analytical method,Numerical analysis method conducts the system research,and combined with field data conducts a coMPrehensive and systematic comparative analysis on Surface deformation of the project.At last,the following ideas are obtained:Based on the theoretical discussion on the structure of the overlying strata in the working face of the tunnel,the effect of the stratum pre reinforcement including formation stabilizing effect,the effect of the beam arch and the pull rod effect has been summarized,and finally revealed its internal mechanism.Sum up the calculation method of surrounding rock pressure of tunnel,on the basis of this,determined the load of shallow buried and unsymmetrical pressure tunnel,and according to the theory of soil medium idealized theory proposed by Winkler,Established the mechanical model of pipe roof advance support structure.Based on the Dong-Shan tunnel project,the mechanical response of the two types of pipe roof was compared and analyzed.The results obtained from the 1 types of the pipe roof are better than the type 2.Utilizing the finite element software MIDAS GTS NX to simulate and analysis Dong-Shan multi arch tunnel and debated the deformation laws and mechanical response of tunnel pipe roof,surrounding rock and wall structure under the process of construction,which can basically reflect the pipe roof reinforcement influence on surface deformation.The necessary numerical analysis should been carried out beforethe actual construction to control the distribution of the stress and the displacement of the soil.Combined with measured surface settlement data,Comparative analyzed ground surface settlement,vault subsidence and pipe roof mechanical response under the pipe roof reinforcement of tunnel and no the pipe roof reinforcement of tunnel.The results show that the pipe roof reinforcement system in the control of surface subsidence and roof subsidence have good effect;for the stability of tunnel face discussion,revealing the strata longitudinal displacement deformation trend of tunnel working surface under pipe roof reinforcement.Using Matlab programming procedures and Midas gts nx numerical analysis software to discuss factors contain pipe roof length,diameter,the distance between the rows,excavation footage and the layout of the form which impact on tunnel pipe roof reinforcement effect under the different conditions,carried out quantitative analysis of the relationship between the parameters and the effectiveness of advance support,provided the corresponding reference value;given a shallow buried tunnel pipe roof pre reinforcement parameters design method assisted with engineering practice.