Research On Dynamic Problems Of Long-span Tunnel Against Earthquake Loading

With the rapid development of society,people have the demands for convenience,comfort and safety performance in transportation.The development of transportation has not been limited to the above-ground structure,More and more urban underground space and subsea tunnels have been put into use.In the past,the structure of underground tunnel was considered to have excellent seismic capability,but with the appearance of tunnel earthquake disaster data in recent years,the seismic response mechanism and destructive modes of tunnel structure are more complicated,and there will cause huge potential safety hazards for continuous use with tunnel structure which have damage or slightly damage under earthquake.So that,it is of great significance to study the dynamical problems of tunnel under earthquake.The research of this paper is based on the National 973 Qiongzhou strait shield tunnel project which named "Structure Design Theory and Safety Evaluation of Shield Tunnel under High Water Pressure",introducing the virtual excitation method of non-stationary random vibration and dynamic boundary element method into the research on dynamic problems of long-span tunnel against earthquake loading.This paper has done the following works.First of all,the structure of the tunnel and its research methods against earthquake were fully investigated.The earthquake action mechanism and seismic dynamic behaviors of the tunnel were sorted out.The history of seismic research on tunnels,the commonly used research models and research methods were briefly introduced.Secondly,the longitudinal dynamic response of the tunnel under earthquake is studied.A pseudo excitation method for the non-stationary random vibration analysis of tunnel-soil coupled structures is developed.Compared to the traditional random vibration CQC method,the computational efficiency is greatly improved.The time-varying standard deviation of the mid-span bending moment for tunnel and the power spectrum along the tunnel length under non-stationary excitation indicate that the dynamic response of the structure is closely related to the modulation function of the non-stationary excitation and significantly affected by different boundary conditions.Thirdly,Bearing capacity calculation and reliability analysis of the cross-section of the tunnel under static loads was studied.The universal finite element program was used to establish a finite element model of cross-section of the shield tunnel.Taking into account loads such as earth pressure and water pressure,the law of the internal forces of the tunnel lining structure is analyzed.Checking the dangerous location of the structure that may be damaged,and analyzing the structural reliability using the probabilistic analysis module when the parameters such as lining stiffness are random variables.This works can lay the foundation of the dynamic analysis of tunnel under the actual earthquake.Finally,the dynamic response of the cross-section of the tunnel under earthquakes was studied.Based on the advantage of reducing orders in dealing with semi-infinite domain problems for boundary element method,using Laplace transform domain algorithm to change the time variable into the transform domain,there will obtain the solution in time domain through reverse change.Furthermore,the dynamic response of the tunnel structure considering the parameters with uncertainties is discussed,the improved second-order perturbation method is used to analyze the parameters uncertainties.The Monte Carlo sampling method is used to verify the calculation results,and it shows better effects.