Study On The Deterioration-Dissipative Mechanism And Prevention Method Of The Bearing Performance Of The Lining Structure In The Service Tunnel

With the rapid development of China's engineering construction,the number of tunnels is increasing.As the structure of the underground space,the tunnel is buried in the formation for a long time.The engineering geology and hydrogeological conditions are complex and changeable.In view of the limitations of the design,construction and operation management experience of the early tunnel,there are a large number of structural diseases of different degrees in the existing tunnels.Among them,the problem of lining cracking is particularly prominent.In the face of the "sick service" of the tunnel that is about to exist,the study of the deterioration-dissipation mechanism and the prevention and control method of the tunnel lining structure will have great theoretical value and practical engineering significance.Based on the renovation and maintenance engineering of the eight Panshan tunnel,based on the detailed field investigation and statistical data,combined with the finite element simulation,this paper makes an in-depth study on the deterioration dissipation mechanism and the prevention and control method of the carrying capacity of the in-service tunnel,and the main research contents and results are as follows:1.According to the investigation and statistics of the condition of the lining cracking of the eight Panshan tunnel lining,this paper introduces the methods and contents of the site detection of the lining crack damage,expounds the types,distribution and quantitative description of the lining cracks in detail,and summarizes the damage of the lining crack and the main causes.2.The deterioration mechanism of concrete structure in four aspects of carbonization,harmful ions,alkali aggregate reaction and freezing thawing cycle is analyzed.The basic principles of linear elastic fracture mechanics and elastoplastic fracture mechanics are introduced.The basic theory of crack loss and dissipation of lining structure is expounded,and the extension finite element based on Abaqus is demonstrated.The principle of element analysis is used to analyze the reasonableness of the lining structure.3.The finite element calculation model of tunnel lining structure of lossless and cracked tunnel is established by using Abaqus software.The bearing performance and stability of the lining structure are analyzed and studied,and the stress characteristics of the lining structure and the regularity of the stability are obtained.4.The existing qualitative and quantitative evaluation criteria for tunnel lining structure are summarized.On the basis of this,combined with the previous finite element analysis,the critical depth 15 cm of the crack is taken as a supplementary index,the original evaluation criterion is amended,and the safety assessment mark of the similar project of the eight Panshan tunnel is put forward.According to the actual cracking condition of the eight Panshan tunnel lining,a detailed regulation and maintenance plan is made.