Study On Large Deformation Mechanism And Support Control Of Sericite Schist Tunnel In Western Yunnan

In this paper,based on the Project of The Baishitou tunnel of Dalin Railway,by means of theoretical analysis,laboratory test,numerical calculation and field test,the problem of large deformation during the construction of the sericite schist section of the White Stone tunnel is studied in depth,and the supporting measures of the large deformation tunnel are optimized.The specific research contents of this paper are as follows:(1)The mineral composition,uniaxial saturated compressive strength and in-situ stress environmental conditions of the surrounding rocks in the sericus schist section of The White Stone tunnel were determined by indoor and outdoor tests.(2)by a white silk mica schist stone tunnel surrounding rock deformation and stress of surrounding rock and early contact with the surrounding rock pressure monitoring result is analyzed,combined with the large deformation section of the supporting structure of macro failure character,summarized silk mica schist,the characteristics of large deformation and failure of tunnel,and in combination with the practical situation of relying on the tunnel construction site,large deformation degree of extrusion of silk mica schist is identified and divided the large deformation level.Considering the engineering characteristics of surrounding rock and the macroscopic characteristics of large deformation,the main influencing factors causing large deformation of sericite schist tunnel are analyzed,and the variation law of stress and strain of surrounding rock with time obtained by theoretical analysis is combined,and the large deformation mechanism of sericite schist section of white stone tunnel is put forward.(3)according to the silk mica schist large deformation of tunnel geological situation,using the finite difference calculation software FLAC3D three-dimensional numerical model is set up,the advance support,steel anchor pipe,prestressed arch,lock foot resin anchor rod support measures such as optimized analysis,the different advanced small pipe layout parameters and lock foot arch model,different length and different length of prestressed anchor resin anchor rod’s influence on the deformation of tunnel surrounding rock.In addition,the application effect of prestressed resin bolt in large deformation section is discussed through monitoring and measuring data and field drawing force test.(4)Field co MParative analysis tests were carried out in sericite schist section of Baishitou tunnel,and the deformation of surrounding rock,surrounding rock pressure,steel arch stress and contact pressure between primary support and secondary lining under different supporting parameters were obtained.The field monitoring results verify that the optimized support measures have a significant effect on controlling the large deformation of sericite schist tunnel.