Study On Time-varying Reliability Calculation Method Of Existing Tunnel Lining Structure

Certain mechanical parameters of the tunnel body structure will degrade over time during the tunnel operation,which will seriously affect the reliability of the tunnel structure.In this paper,the time-varying reliability analysis of the tunnel structure based on the deterioration effect is carried out,starting with the deterioration of the performance of the lining structure of the operating tunnel.The main results of this paper are as follows:(1)For concrete lining,there are many failure modes in the structure due to the interaction of many time-varying factors in the service process.For this reason,a time-varying reliability analysis method for tunnel lining structures in service based on resistance attenuation control,maximum crack width control and concrete carbonation depth control was proposed.The reliability analysis model of lining multi-failure mode system was constructed by using probabilistic fault tree model,and the reliability index and failure probability of structure were calculated by JC method.The influence of different failure modes on the reliability of lining structure was analyzed.(2)In view of the difficulty of obtaining accurate data information in reliability evaluation,the interval non-probabilistic reliability model was applied to the reliability analysis of tunnel lining structure,and the time-varying reliability theory was combined.A nonprobabilistic time-varying reliability model of tunnel structure was presented.The variation rule of reliability during the service period of lining structure and the influence of different attenuation function on reliability were analyzed.The reliability level and variation law of the reaction structure can be reasonably obtained by the model.It provides a scientific and reasonable reference method for the reliability evaluation of lining structure during the service period.(3)Using agent model to approximate implicit limit state function,a reliability analysis method based on Kriging model was proposed.In view of the lack of precision of test sample points in structural reliability analysis using Kriging model in the past.A method for calculating the reliability of Kriging model using Hammersly point set to construct sample points was proposed.The method was applied to engineering examples,and the validity of the method was verified by changing the number of sample points and the number of iterations.The accuracy of the method was verified by comparing it with Monte Carlo method.By designing the sample points of random variables,the linear relationship between reliability index and random variable was fitted by least square method,and the factors of structural reliability index of each random variable under both compressive and tensile conditions were solved.(4)Based on time-varying reliability theory,the maximum crack width criterion and ultimate bearing capacity criterion were used to predict the service life of tunnel lining structure.The gradual relationship of bearing capacity reduction due to durability reduction was described.Through the calculation of the reliability of tunnel design years,that is,during the service period,the reliability of the structure was verified by combining the target reliability to verify whether the structure meets the design requirements.According to the comparison results of structural service life prediction under two kinds of life criteria,the service life prediction value under crack limit criterion was smaller than that under bearing capacity criterion,and the result accords with the actual engineering situation.