| The topography and geological conditions in the western part of China are complex.In the tunnel construction process,it is often necessary to cross the poor water area,fault fracture zone and other unfavorable geological areas.During the construction process,the tunnel is prone to local collapse,large deformation and water inrush.Therefore,in order to ensure the safe excavation of tunnels in unfavorable geological sections,it is necessary and urgent to study the pre-reinforcement technology before tunnel excavation and the construction method and support structure during excavation.In this paper,the Qinyu bad geological section tunnel is taken as a research example.Combined with the meteorological and hydrological conditions,topography and geomorphology,geological features of the tunnel and the mechanism and scope of the pre-reinforcement technology,the pre-reinforcement scheme of the Qinyu bad geological section tunnel is proposed.The possibility of water inrush during tunnel excavation,the simplified calculation model of the maximum water inflow in Qinyu tunnel was established,and the pre-reinforcement scheme for tunnel excavation in Qinyu bad geological section was proposed,and the construction method and support scheme of the tunnel were optimized.The stability of the tunnel is analyzed by dynamic monitoring.Finally,the finite element software is used to analyze the stress and deformation of the tunnel surrounding rock under hydraulic coupling and the stress characteristics of the lining structure.The deformation characteristics of the tunnel under hydraulic coupling are obtained by comparing the tunnels with the force field.Specifically:(1)The mechanism and application scope of the pre-reinforcement technology are analyzed in detail.Combined with the characteristics of the bad geological section of Qinyu tunnel,the pre-reinforcement scheme combining the hole of the Qinyu tunnel and the pipe shed through the extremely broken surrounding rock section,the lead small pipe and the anchor rod is proposed.And the specific embodiment optimizes the length,inclination and grouting amount of the anchor;(2)Based on the meteorological and hydrological conditions,topographical features and unfavorable geological structure of Qinyu tunnel,the possibility of water inrush from the tunnel of Qinyu bad geological section is analyzed,and the simplified calculation model of the maximum water inflow in Qinyu tunnel is established.The maximum amount of water inflow in the tunnel is compared withthe measured value at the time of tunnel excavation.It is concluded that the calculated result of this method is close to the actual measured value;(3)Proposed preventive measures for local collapse and large-scale water inrush in Qinyu bad geological section,and forecasted and predicted real-time dynamic monitoring schemes during tunnel excavation,combined with on-site dynamic monitoring data to analyze the excavation of Qinyu tunnel Deformation of the retaining structure and stability of the tunnel;(4)The calculation model of tunnel excavation under hydraulic coupling is established by using finite element software.The stress and deformation characteristics of the tunnel support structure under the action of seepage field and force field are analyzed,and the tunnel support structure is used when the force field acts alone.The comparative analysis of the force and deformation gives the difference of the force and deformation characteristics of the structure,which provides guidance for tunnel excavation in the water-rich area. |
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