Research On Seismic Response Law Of Canyon Under Oblique Incidence Of Seismic Wave

In recent years,with the overall promotion of the Sichuan-Tibet railway construction in my country,the construction of the Sichuan-Tibet line has become an important project in the national infrastructure.The Sichuan-Tibet area has a complex geological environment,spans a wide area,and passes through multiple seismic zones on the way,and the site conditions are complex.The seismic intensity is high and earthquakes occur frequently,and it is difficult to avoid in the construction of railway projects,which brings huge challenges to the construction of the Sichuan-Tibet railway.According to the investigation,most sections of the Sichuan-Tibet line are located in high mountains and river valleys,with high mountains and deep valleys along the line,and there are many canyon topographies,which will make seismic amplification effect severe.There are many faults along the Sichuan-Tibet line,and the oblique incidence of seismic waves has a great influence on the surface seismic response of inconsistent structures,and the incident angle of the seismic wave is uncertain.So it is necessary to consider the research on seismic response law of canyon under oblique incidence of seismic wave.At present,The seismic response analysis of canyon topography usually assumes that the seismic wave is incident vertically,but for shallow earthquakes,the seismic wave usually has a certain angle when it reaches the ground surface.The analysis of the canyon topography under the action of vertical incident seismic waves is not comprehensive.Therefore,the paper analyzes the study of the seismic response law of the canyon topography under the action of obliquely incident seismic waves.The specific research contents and results are as follows:1.With the help of finite factor software ABAQUS,numerical simulation calculation is carried out,the wave input of the viscoelastic artificial boundary is carried out by the equivalent node force.The different incident angle inputs of P-wave and SV wave are realized.The calculation formula of the boundary equivalent node force under the action of two-dimensional plane P-wave and SV wave is derived.The program of automatic addition of equivalent node force is written,and the input method of seismic wave is verified.2.Based on the above method,the paper analyzes the canyon topography in seven aspects including different aspect ratio,depression angle,medium parameters,cover layer thickness,depression shape,number of depressions,and net spacing of depressions,and it obtains surface monitoring of depression models under different P wave and SV wave incidence angles point displacement amplitude,the result shows:(1)The depth-to-width ratio of depressions,the angle of depressions,and the material parameters have a relatively stable effect on the site effects under the action of P-wave and SV-wave.With the increasing depth-width ratio of the canyon topography,the variation of the displacement amplitude of the canyon surface monitoring point gradually increases,the displacement value of the sunken surface monitoring point is relatively small at the depression angle 45°,the site effect of soft soil material is significantly amplified under the action of P-wave and SV wave,and the site effect of hard soil material under the action of P wave and SV wave is reduced.(2)The effect of the cover thickness,depression shape,number of depressions,and net spacing of depressions on the site effect under the action of P-wave and SV wave depends on the P-wave and SV wave incident angle.The thickness of the covering layer,the shape of the depression and the net spacing of the depression have a significant effect on the displacement value at the concave vertex.The site effect of the rectangular canyon topography is more significant than that of the semi-arc and V-shaped canyon topography.There is some difference between the displacement amplitude of multiple canyon topography and the single canyon topography,and the displacement value of the monitoring point is basically increasing with the gradual increase of the net spacing of the depression.(3)With the increase of P wave incident angle,the horizontal displacement amplitude gradually increases,the vertical displacement amplitude decreases gradually,and with the increase of SV wave incoming angle,the horizontal displacement amplitude decreases gradually,and the vertical displacement amplitude increases gradually,but due to the difference between P wave and SV wave in vertical incident and oblique incident,resulting in special cases.Under the condition of seismic wave oblique incident,the existence of canyon topography makes seismic wave shielding effect,which causes the left and right displacement amplitude to be enlarged or reduced effect,and the oblique incident of seismic wave should be considered when studying the site effect.