Research Of Site Response Considering Uncertainty

The site seismic response analysis is the main research content of geotechnical engineering.It provide earthquake motion input for ground buildings and give the parameters like acceleration and displacement of the site.The influence of uncertainty on seismic response analysis can not be ignore.According to the existing soil layer response analysis method,There are two main sources of uncertainty,One of them is the uncertainty of the choice of the numerical simulation method,and the other is the uncertainty of the soil layer parameters of the site.China Earthquake Science Experiment Field（CESE）plan to build a ground earthquake motion observation system for complex engineering sites in Xichang area.The purpose is to deepen the understanding of the transmission law of ground earthquake motion in the field.This paper is based on survey and measured data in CESE Xichang area.Comprehensively consider the effects of method and parameter uncertainty on site seismic response,provide theoretical and technical support for the construction of CSES.This paper mainly completes the following work:1.Base on the results of Vs blind test in Xichang area,143 parallel blind tests of Vs were carried out in 8 shallow boreholes at 40m depth and 5 deep boreholes at 100m depth.Obtained the statistical results on Vs,built a statistical model to describe the uncertainty of Vs.2.According to the results of peak acceleration along the depth calculated by DEEPSOIL,SHAKE2000,SOILQUAKE,SOILRESPONSE（simplified version）.（1）The calculation results of the four programs are different,and this difference increases with the increase of the input ground motion.（2）When considering the uncertainty of V_S,under the small seismic input,the influence of uncertainty on the internal seismic motion of the site is not obvious,and with the increase of the seismic input,the change of SOILQUAKE calculation result is significantly greater than the other three programs,and the discrete change of DEEPSOIL and SOULQUAKE calculation results becomes significantly larger.3.When considering the uncertainty of methods and V_S.the results show that both PGA and coefficient of variation increase with the increase of input seismic.When the input ground motion is aend050-63,the calculation results of the four programs are same;Wnen the motion input increases,the SHAKE2000 calculates the PGA and its coefficient of variation is smallest.The PGA results calculates by DEEPSOIL is similar to SHAKE2000,but has a large coefficient of variation.The PGA results calculates by SOILRESPONSE（s）is bigger than SHAKE2000 and DEEPSOIL,Also has a small coefficient of variation.SOILQUAKE’s calculated PGA and coefficient of variation are the largest of the four calculation programs4.The dynamic amplification factor spectrum is used to represent the standardized design response spectrum after calibration.Comparing the values and variation coefficients of T_g andβ_max calculated by four programs.The results show that the coefficient of variation and value of T_g andβ_max increase with the increase of the seismic input ground motion.The change amplitude of shallow boerhole is small and the variation of deep boerhole is larger.In shallow boerhole,SOILRESPONSE（S）and SHAKE2000increased significantly,while DEEPSOIL and SOULQUAKE increased significantly,which was greatly affected by uncertainty;...