| Muzhailing tunnel of Lanyu Line is located in Gansu province,which is named "extremely high risk tunnel" by the Ministry of Railways.When tunnel is constructed through ridge section,it experienced large compressional deformation because of high ground stress with the maximum principal stress measured 38.38 MPa combined with the weak surrounding rock,which makes the construction of the primary support changing constantly and the secondary lining cracking frequently.It has seriously threatened the safety of secondary lining structures.This paper takes Muzhailing tunnel as the research background,combined with the site construction conditions,the mechanical characteristics,lining conversion technology and safety assessment of lining structure for tunnel in soft rock with high geostress are researched by using the finite element software,theoretical and numerical analysis and monitoring measurement method.This paper has done the following research:(1)Through literature research and analysis on the field measured data,the second lining cracking situation of curved walls in the early period is collected,based on which the lining cracking characteristics of ridge segment are concluded.And the reasons of lining cracking are analyzed through the numerical simulation and theoretical analysis.(3)The lining crack control technology of curved wall segment during early stage is proposed,and the mechanics and deformation characteristics of surrounding rock and support structure have been comparised before and after changing lining through the field monitoring and numerical simulation methods,thus the safety of lining is evaluated.(4)For the large deformation of surrounding rock and primary support and the high stress of support structure of ridge section in the early period of construction,the construction method of expanding the circular pilot drift is proposed.The stress of support structure is monitored,and its characteristics are analyzed through the field monitoring data,thus the distribution of ground pressure in the supporting structure is obtained.(5)Through regression analysis on the contact pressure of primary support and second lining of the circular pilot drift enlarged section,the regression equation of the contact pressure of second lining at different positions is obtained,through which the second lining contact pressure development tendency can be predicted.Taking it as boundary conditions,the safety of secondary lining during the service life can be judged through the load-structure finite element model and stratum-structure model.This paper carries on the research mainly depended on the existing problems in practical engineering,and the research results have been applied well in the field,which can provide reference for future similar projects. |
PDF Full Text Request