Research On Safety Threshold Of Vibration Velocity Of Existing Tunnel Considering Aging Deterioration Of Lining

Tunnel lining concrete structure will deteriorate during the service period,which will change the physical and mechanical properties of concrete structure,reduce the reference value of the original blasting vibration control standard,resulting in the misjudgment of blasting design and construction,and endanger the safety of the existing tunnel lining structure.In recent years,with the increase of existing tunnel projects with small clean distance,upper and lower penetration,it is particularly important to study the safety threshold of vibration velocity of existing tunnel under the influence of deterioration factors.Considered in this article,therefore,the deterioration of concrete and the explosive stress wave in the transmission and reflection of different structure surface,free surface propagation law,on the basis of the limit tensile stress criterion based on the lining concrete structure,maximum shear stress criterion and Mohr-coulomb criterion,establish both tunnel lining concrete structure safety vibration velocity threshold time-varying function model.By means of theoretical derivation,numerical analysis and field measurement,the safety threshold of blasting vibration speed of existing high-speed railway tunnel lining concrete structure and the change rule of vibration velocity safety threshold with time under the influence of concrete deterioration are studied.The main work carried out in this paper includes:(1)Based on the lining structure of concrete ultimate tensile stress criterion,the ultimate shear stress criterion and Mohr-coulomb criterion,and consider the explosion stress wave in the transmission and reflection of different structure surface,free surface propagation law and concrete material degradation,on the basis of establishing both the tunnel lining concrete structure safety vibration velocity threshold time-varying function model.(2)By fitting the measured vibration velocity with Sadowski formula,the attenuation law of blasting peak vibration velocity is obtained.Based on the existing Guangzhou-Shenzhan-Hong Kong Yangtaishan tunnel project in Bogongao No.1 tunnel of ganzhou-Shenzhen passenger dedicated Line,a THREE-DIMENSIONAL numerical model was established by using ANSYS/LADYNA to explore the variation law of peak vibration velocity of the existing tunnel lining structure under different stress wave incidence angles.The reliability of the three-dimensional model is verified by comparing the theoretical calculation results with the numerical simulation results.(3)Based on time-varying safety vibration velocity threshold function model,serving for different time points under different stress wave incident Angle and the adjacent existing tunnel blasting vibration velocity safety threshold analysis,determine both the tunnel lining structure under different conditions of vibration velocity safety threshold,and the vibration velocity safety threshold value and the changes of stress wave Angle,And the law of the change of vibration velocity threshold with the increase of tunnel service time is studied.(4)Through the establishment of three-dimensional numerical calculation model of the different working conditions,for both the sheep taishan tunnel lining concrete structure a numerical simulation of the vibration velocity safety threshold determined at different time points to serve both simulated tunnel vibration velocity threshold value,simulated by vibration velocity safety threshold value and time-varying function theory calculation value contrast,The validity of the time-varying function model of vibration velocity threshold is verified.(5)Based on the linear fitting method,the simulation results and theoretical calculation results of the safety threshold of vibration velocity at different time points were studied to determine the time-varying rule of the safety threshold of vibration velocity in the service period of the existing tunnel.