Mechanical Characteristics And Deformation Law Of Four-Lane Tunnel In Phyllite Stratum

Thanks to the introduction of the reform and opening policy,our comprehensive national strength has greatly improved.the transportation industry has also made rapid development,and the advantage of the tunnel has been increasingly revealed.New problems arising from crossing complex geological conditions emerge in endlessly.Soft rock tunnels are one of the typical problems.At present,there are many studies on structural deformation and stress characteristics of soft rock tunnel.But most of them are aimed at small span section or large section tunnel with high-strength rock.There are not much study on the deformation law of large section tunnel with weak surrounding rock.Based on the tunnel named Hongshihe in Ankang,Shanxi Province,this paper sums up the engineering characteristics of soft rock,fully considers the space and time effects of tunnel excavation,then formulates a reasonable monitoring scheme.By analyses the monitoring data,the paper obtains the general deformation law of soft rock tunnel with large-section.This paper numerically investigate the optimum excavation method and grouting reinforcement range for the purpose of guiding and direction for engineering.Aiming at the shallow-buried bias section with high risk coefficient,the deformation characteristics and structural migration law of the tunnel are analyzed by numerical simulation and data analysis.The main research contents are as follows:(1)The difference between geological soft rock and engineering soft rock is distinguished,the physical characteristics and deformation regularity of soft rock are summarized.According to the general law of deformation and failure of soft rock tunnel,this paper describes the failure modes and influencing factors of soft rock tunnel.(2)Combining with the engineering practice and design scheme,a targeted monitoring and measurement schemes have been formulated.Through the analysis of a series of monitoring data,the deformation characteristics of large cross-section phyllite tunnel are obtained.(3)By using simulation software MIDAS/GTS,different construction excavation models of large-section phyllite tunnel are established.On the basis of considering project quality,costs and current construction condition comprehensively,the excavation method suitable for the soft rock tunnel is selected.Grouting reinforcement are adopted to reinforce the surrounding rock,and the grouting scope with the best reinforcement effect is selected.(4)Based on the results of numerical simulation and deformation monitoring,the structural deformation law of shallow-buried eccentric section of large-section phyllite tunnel is discussed.By analyzing the convergence of tunnels under different migration conditions and the variation law of unilateral displacement,the functional relationship between the displacement and time is obtained.On this basis,the horizontal deformation of steel arch is calculated.