Study On Construction Deformation Prediction And Large Deformation Classification Standard Of Muzhailing Tunnel Of Weiwu Expressway

Large deformation of surrounding rock is common in tunnel construction at home and abroad,which brings great troubles to tunnel builders and is also one of the main research directions of scholars.This paper takes Muzhailing Tunnel of Weiwu Expressway as the research background.According to the actual large deformation of the tunnel in the construction site,the prediction analysis and classification criteria of large deformation of the tunnel are mainly studied by field investigation,theoretical analysis formula calculation and numerical simulation analysis method.The main research work and conclusions are as follows:(1)The engineering background of the paper is introduced,including the engineering design,geological conditions,in-situ stress distribution of Muzhailing Tunnel,the fault crushing zone through which the tunnel passes.According to the field displacement measured data,it is found that the surrounding rock of the tunnel has the characteristics of large deformation,fast deformation rate and long deformation duration.This paper summarizes the following characteristics of construction deformation of carbonaceous slate tunnel: 1)carbonaceous slate has weak expansibility;2)plastic extrusion deformation;3)large deformation and non-convergence;4)construction disturbance sensitivity;and 5)jumping.(2)According to the actual surrounding rock condition of Muzhailing Tunnel and on the basis of existing research results,the characteristics of carbonaceous slate are analyzed from three aspects of Engineering characteristics,mechanical theory and failure mechanism of weak surrounding rock,and the deformation or failure of surrounding rock easily occurs under adverse geological conditions.Slip failure occurs in layered rock mass only when the three conditions of joint and fissure development,failure of interlayer bonding and suitable dip angle are satisfied simultaneously.When the support is not timely or unreasonable,the broken loosening circle of surrounding rock will continue to develop from the excavation face to the inside of surrounding rock,which may lead to large-scale collapse.The mechanical properties of carbonaceous slate and the large deformation mechanism of slate tunnel are analyzed in depth,which provides a theoretical basis for the study of large deformation of carbonaceous slate tunnel.(3)Based on rock mechanics theory and considering rheological characteristics of surrounding rock,the generalized Kelvin creep model equation is used to calculate the horizontal convergence deformation and vertical settlement deformation of the main section of deep buried tunnel under high geostress.The prediction of large deformation of tunnel is carried out according to the calculation results.(4)On the basis of theoretical calculation and analysis,the large deformation of Muzhailing Tunnel is simulated by numerical simulation analysis method.The horizontal convergence deformation and vertical settlement deformation of Muzhailing Tunnel under high geostress are calculated,which are in good agreement with the large deformation in the actual tunnel construction process.Through the data collation and regression analysis,the Muzhailing Tunnel is clearly defined.The stress and deformation law of the tunnel under high in-situ stress is studied,and the data are fed back to guide the practical application of the project.(5)Combining with the practice of Muzhailing Tunnel Project,this paper analyses the basic characteristics and deformation influencing factors of large deformation tunnel,divides the classification standard of large deformation of Muzhailing Tunnel into two stages: theoretical pre-judgment classification standard in design stage and site judgment classification standard in construction stage,and gives the deformation control countermeasures and suggestions for large deformation tunnel construction,which can be used to guide construction.