Study On The Morphology Development Of Tunnel Lining Cracks Under Earthquake

Due to the influence of various factors,the tunnels that have been built in China will produce a variety of diseases.Among them,lining cracks are the most common form of disease,which will endanger the safety of tunnel structure.When studying the tunnel,considering the influence of lining cracks can be closer to the engineering practice.China is a country with many earthquakes,and the influence of earthquake on tunnel lining cracks is particularly important.In this paper,the tunnel lining structures with different buried depths and cracks in different directions are studied.The deformation,stress and morphological development of lining cracks under earthquake action are studied by combining indoor model test and numerical simulation.The main research contents and conclusions of this paper are as follows :(1)The research status of tunnel lining cracks at home and abroad,the relevant data of tunnel structure seismic and underground engineering are collated and analyzed.The causes,classification,classification and characteristics of tunnel lining cracks are summarized.Through the analysis of the existing tunnel site survey results,it is found that the largest number of tunnel lining cracks is circumferential cracks,followed by longitudinal cracks,and the number of oblique cracks is the least.The proportion of cracks in the arch waist is the largest,followed by the vault.(2)Using the method of indoor model test,design appropriate test scheme and test conditions.According to the test conditions,shaking table model tests were carried out on tunnels with different buried depths and linings with different crack directions.It was found that the expansion of longitudinal cracks was the largest under seismic action.It is concluded that the earthquake has the greatest influence on the lining structure with longitudinal cracks,followed by the lining with oblique cracks,and has the least influence on the lining structure with circumferential cracks.The direction of fracture development is to continue to develop along the initial direction with about 15 deviations.(3)The model of surrounding rock and tunnel lining is established.FLAC3 D software is used to simulate the cracks of tunnel lining under different working conditions,and the deformation and stress changes in the calculation results are analyzed.The results show that the existence of tunnel lining cracks has an effect on the deformation and stress distribution of lining structure.Compared with the tunnel lining structure under natural state,the tunnel lining structure with cracks under earthquake has larger deformation and the deformation is concentrated around the cracks.Among them,the longitudinal crack has the largest deformation,followed by the oblique crack,and the circumferential crack has the smallest deformation,which is not much different from the non-destructive lining structure.Under the action of earthquake,the deformation of the bottom of the tunnel is the largest.(4)Comparing the model test results with the numerical simulation results,it is found that the seismic action has the greatest influence on the longitudinal cracks,followed by the oblique cracks,and finally the circumferential cracks.When the cracks are treated,the longitudinal cracks can be treated emphatically,and the direction of the rock crack tip can be 15°.