Study On Earthquake Effect Of Valley Site In Mountainous Areas

The earthquake damage investigation showed that the seismic topography effect of the river valley site was significant,causing more serious economic losses and casualties.Scholars at home and abroad have carried out fruitful research on the ground motion effects of river valley sites,and have obtained a clear qualitative understanding,which provides an important reference for the seismic design of such sites.However,how to quantitatively consider river valley site effects in seismic design is still unclear.However,how to quantitatively consider the effect of river valley site in seismic design has not been well resolved,which brings potential risks to the seismic design of river valley site buildings(structures).(1)The existing research results of ground motion effects of river valley sites are reviewed.Based on this,a typical bedrock and a typical river valley site with an overburden layer were selected,and a centrifuge shaking table test of the ground motion effect of the river valley site was designed and carried out.Ground motions of different intensities and spectral characteristics were input to obtain the bedrock and soil Ground motion characteristics of the ground floor.(2)The constitutive relationship,boundary conditions,material parameters and key links of the damping form selection of the finite difference software FLAC3D are described.The numerical model of the typical river valley site corresponding to the centrifuge shaker model is established,and the results are compared with the centrifuge shaker model test results.By comparison,the reliability and rationality of the established FLAC^3Dnumerical analysis model was verified,and the seismic response law of the valley site was further given.(3)Based on the verified FLAC^3D numerical analysis model,the four influencing factors of inputting different ground motion spectrum characteristics,ground motion intensity,site slope angle and aspect ratio were expanded and studied.The orthogonal test table was designed,the calculation conditions were determined,and the ranking of the influencing factors of the slope top section,slope section and valley bottom section at different locations of the river valley site was obtained.Then,the response spectrum results of different numerical simulations were compared and analyzed for preliminary results.The adjustment coefficient of the magnified spectrum of the river valley site is shown.