Health Evaluation And Influence Of Disease Stability Of Operational Highway Tunnel Structure

With the increasing investment in transportation infrastructure construction,China has become the country with the largest number of tunnel projects,the most complex structure and the fastest development speed in the world.However,under the influence of adverse conditions,such as the change of geological conditions,the operation environment,the restriction of design level and the lack of construction technology,various structural diseases will inevitably appear after the tunnel operation for a period of time,such as lining cracks,voids behind the lining,leakage and so on.However,structural diseases often lead to significantly reduced durability,bearing capacity and service time of tunnels,which seriously affect the health of tunnel structures.In order to scientifically evaluate the impact of structural diseases on the health state of tunnel structures,it is necessary to first accurately evaluate the health state of tunnel structures and further study the impact of typical and widely developed structural diseases on the stability of tunnel structures,then propose targeted disease control measures.This paper has important theoretical value and practical significance for the healthy maintenance,scientific management and continuous development of highway tunnel.Based on this,this paper firstly analyzes the deficiencies of the existing tunnel disease classification standards in detail.According to the disease factors influencing the health state of the operating tunnel structure,the fuzzy hierarchical comprehensive evaluation method is adopted to build a qualitative and quantitative evaluation index system,which lays a theoretical foundation for proposing a multi-factor and multi-index linkage health evaluation method of highway tunnel structure during the operating period.Secondly,the software of tunnel structure health evaluation system is developed and applied with engineering example.Finally,aiming at two typical structural diseases in the evaluation results,namely lining cracks and voids behind lining,the influence of the disease stability was studied by model test,numerical simulation and theoretical calculation,and the corresponding disease control measures were proposed according to the research results.The main research work and conclusions are as follows:(1)Combined with the classification methods of tunnel lining structure health status and the characteristics of highway tunnels,a four-level classification method of highway tunnel structure health status was developed.Based on the existing research results and industry norms,six typical structural diseases were selected as first-level indicators,17 measuring parameters were selected as second-level indicators,and a comprehensive evaluation system for the structural health of operating highway tunnels was established.(2)According to the characteristics of diagnostic index weights in tunnel structure health diagnosis index system,product scaling method and entropy weight method were used to determine the weights of evaluation indicators.This paper analyzes the shortcomings of the existing tunnel structure health evaluation criteria,and introduces fuzzy mathematics membership degree and membership function optimization evaluation criteria to make the evaluation results more reasonable.According to the defects of the existing evaluation methods,the short-plate theory was introduced into the whole tunnel structure health evaluation system,and the tunnel structure health evaluation process was proposed,namely the division of target tunnel units,the selection of evaluation data,the comprehensive evaluation of single evaluation unit structure health and the comprehensive evaluation of the whole tunnel structure health.(3)The tunnel structure health evaluation system is developed by using Matlab software tool.The system includes three modules: weight calculation,weight result and comprehensive evaluation,which can realize the rapid and reasonable classification of tunnel structure health status.The comprehensive evaluation on the lining structure health of SK0+800-SK0+900 section of Wushan tunnel shows that the cracks and voids behind the lining are grade Ⅲ,and tend to develop to grade Ⅳ,which are typical and serious structural diseases.According to the most unfavorable principle,the structural health comprehensive evaluation grade of SK0+800-SK0+900 section of Wushan tunnel is finally determined to be Ⅲ,that is,the structural damage is serious.The countermeasures and suggestions are to focus on monitoring the damaged parts of the structure and implement the disease treatment measures as soon as possible.The evaluation results are in good agreement with the actual situation on site.(4)According to the typical diseases of lining cracks in the evaluation results,the self-made 1: 10 large scale model test and numerical calculation method were used to study the influence of different length,number and direction of lining cracks on the mechanical characteristics of lining structure,and the influence law of lining cracks in different working conditions on the stability of lining structure was analyzed.The results show that the lining cracks will cause stress concentration,and the stress will increase with the development of the lining cracks.When there are cracks in the lining arch,the security coefficient of the arch and the sprue will decrease obviously.The internal force of lining structure is increased by cracks in different directions,and the influence of longitudinal cracks on the stability of lining structure is more significant.When the vertical distribution pressure reaches 0.302 MPa and the horizontal distribution pressure reaches 0.151 MPa,the bottom crack of the lining vault first begins to crack.(5)Aiming at the typical diseases of voids behind lining with high evaluation grade,model test and model calculation methods were used to study the influence of voids behind the lining at different depths,lengths and positions on the mechanical characteristics of the lining structure,and the influence law of voids behind the lining under different working conditions on the stability of the lining structure was analyzed.The results show that the stress of lining increases with the development of void behind lining.The void behind the lining increases the internal force of the lining structure,and the void depth has a more significant effect on the stability of the structure.The security coefficient of lining structure decreases with the increase of void depth,and the security coefficient of vault position decreases most obviously.Under the action of ground stress,when the vertical uniform distribution pressure q=0.584 MPa and the horizontal uniform distribution pressure e=0.292 MPa,the fracture occurred at the inner wall arch of the lining.(6)Based on the typical structural diseases of highway tunnel,the causes and treatment measures of the lining cracks and the voids behind the lining in the health evaluation system are analyzed,and the maintenance and reinforcement of Wushan tunnel are carried out according to the proposed treatment measures.Then,through theoretical analysis and numerical calculation method,the treatment effect of the tunnel reinforcement scheme of "lining with anchor and bolt hanging net with steel fiber reinforced concrete" under the condition of ground stress during operation period is studied.The results show that,compared with before reinforcement,the structural stress of the tunnel is significantly reduced,the security coefficient of the lining is significantly increased,and the overall safety of the tunnel is effectively improved,reaching the safety standard.