Dynamic Response Characteristics And Seismic Stability Of Weak Surrounding Rock Slope With Double-arch Tunnel

At present,with the development of infrastructure construction in China,a large number of tunnels have been built in China.A considerable part of the tunnels are located in the strong earthquake area in the west of China.In many tunnels,as a kind of tunnel form,the multi arch tunnel has the characteristics of large passage area and small land area.It has obvious advantages in the situation of tight urban land use,complex geological conditions in mountainous areas,and difficult to expand the line in line design,and has been widely used.Because of the earthquake,the side slope of the tunnel with multi arch suffered serious damage,which brought huge loss to the national economy.At present,the research on the slope of the tunnel with multiple arches focuses on the numerical calculation and construction monitoring,while the research on the dynamic response characteristics and stability of the slope of the tunnel with multiple arches under the earthquake has not been seen in the literature.Different from the common slope,the mechanical environment of the slope is deteriorated by the existence of the multi arch tunnel,which makes the stress situation of the slope more complex under the earthquake power,and also different from the tunnel slope with small clear distance and the tunnel slope with single hole.This paper is based on the project of NSFC(51204125,Based on Wenchuan wave,El Centro wave and Kobe wave,a shaking table test of weak surrounding rock slope with a similar ratio of 1:20 was designed and completed.A three-dimensional numerical calculation model of the slope was established by Midas GTS/NX,and the law of seismic dynamic response and seismic stability of the slope were explored.The research results can be used for reference in the aseismic design of multi arch tunnel slope.The main research contents and conclusions are as follows:(1)Scheme design of shaking table testAccording to the similarity ratio of 1:20 and the similarity theory,the similarity design is carried out.According to the experimental scheme,the boundary treatment method of the model box,the layout scheme of the measuring points and the data monitoring method are determined.The weak surrounding rock slope model of the double-arch tunnel is made by using different materials.According to the engineering practice,the appropriate loading seismic wave is selected and the loading scheme of seismic wave is formulated.(2)Study on seismic response law of weak surrounding rock slope withdouble-arch tunnel based on shaking table model testThrough the shaking table model test,the acceleration and dynamic displacement data of the corresponding measuring points of the weak surrounding rock slope withdouble-arch tunnel are collected.By using the data processing software to sort out and analyze the test data,the seismic response law of the weak surrounding rock slope of the double-arch tunnel with different seismic wave,different excitation intensity and direction is obtained.It is found that with the increase of the relative height of the slope,the acceleration amplification coefficient and the peak value of the dynamic displacement response of the weak surrounding rock slope of the double-arch tunnel show a significant non-linear trend along the slope,and the acceleration amplification coefficient and the peak value of the dynamic displacement response change trend have obvious mutation at the rock interface;the slope rock mass has a filtering effect on the seismic wave.Different ground motion parameters,such as seismic wave type,excitation intensity and direction,have different effects on the acceleration and dynamic displacement response of slope.The results show that the larger the excitation intensity is,the more obvious the seismic dynamic response of the slope is,the stronger the dynamic response of the slope is under two-way excitation,and the different acceleration and dynamic displacement responses of the slope are under different types of seismic wave excitation.(3)Study on seismic response characteristics of weak surrounding rock slope with double-arch tunnel based on numerical simulationMidas gts/nx was used to establish the weak surrounding rock slope model with double-arch tunnel.The data of numerical simulation were collected and compared with the results of shaking table test,which verified the rationality of shaking table test and numerical calculation model.Based on the results of numerical simulation,the variation law of acceleration amplification coefficient of internal measuring points of slope is analyzed,and it is found that the acceleration amplification coefficient of slope has a trend effect.Through the establishment of different numerical calculation models and comparison of the seismic dynamic response of the model,it is found that the seismic dynamic response of the slope with double-arch tunnel is more severe and the stability is worse than that without tunnel;the closer thedouble-arch tunnel is to the slope,the greater the impact on the seismic dynamic response of the slope,the worse the slope stability.It is found that the existence of the double-arch tunnel has deteriorated the mechanical environment of the slope and reduced the slope stability;the closer the double-arch tunnel is to the slope,the more unstable the slope is.By changing the amplitude,frequency spectrum,duration and other ground motion parameters,the influence of ground motion parameters on the dynamic response of slope is discussed.It is found that the larger the amplitude,the smaller the time compression ratio and the longer the duration of the seismic wave,the greater the impact on the seismic dynamic response of the slope,and the stronger the seismic dynamic response of the slope.(4)Seismic stability analysis of weak surrounding rock slope with double-archtunnelBased on the shaking table test results and numerical simulation,the safety factors of slope stability under different types,different holding times,different directions and intensities of seismic wave excitation are calculated.It is found that the safety factor of slope stability under two-way excitation is smaller than that under one-way excitation,and the smaller the safety factor of slope stability under seismic wave excitation with longer holding time and higher excitation intensity is,the more unfavorable it is to slope stability.Through the numerical simulation software to establish different slope models,four kinds of slope protection methods are designed.Through the calculation of slope stability safety factor and other indicators,it is found that under the protection of comprehensive slope protection measures,the safety factor of slope stability is the largest,and the most appropriate measures to improve the stability of weak surrounding rock withdouble-arch tunnel are comprehensive slope protection measures.In the actual project,it is recommended to adopt a combination of multiple slope protection methods Measures.In conclusion,through the design and completion of the shaking table model test of the weak surrounding rock slope withdouble-arch tunnel,the seismic dynamic response characteristics of the slope withdouble-arch tunnel are explored,and combined with the finite element analysis software Midasgts/nx makes a deeper research on the seismic response law of the slope with the double-arch tunnel,discusses the influence of the seismic parameters on the seismic response of the slope;finally,it establishes several slope protection models,and puts forward a slope protection method suitable for the side slope of the tunnel with multiple arches,taking the slope stability safety factor as the main index;it provides a reference for the seismic design and protection measures implementation of the slope with the double-arch tunnel in the future set reference basis.