Study Of Coastal Soft Soil Site Seismic Response Analysis

China is a earthquake-prone country,in the same time,China is one of theearthquake seriously affected countries.For the improper seismic fortification,thestructures suffer huge damage. Especially the eastern coastal areas,for highlydeveloping of economic and high density of population,the indirect or direct loss isinestimable. So the seismic site analysis for the soft soil of coastal area is of highsignificance in engineering and economy.The seismic site analysis consists ofequivalent linear method and non-linear method.The equivalent linear analysismethod,that sets a equivalent damping ratio and shear modulus and reduceparameter,is simplified the calculation and the results are reasonable in smallstrain.The non-linear analysis method takes the character of soft soil,such asnonlinearity and hysteresis, into consideration.This method’s parameter is more thanequivalent linear method’s and it hasn’t a agreed fit method, but its results are moreaccurate.The paper explains the usual analysis methods of foreign or domestic on threeaspects:basic assumption,basic constitutive relation and basic theory. Combiningwith the terra drill data of seismic safety evaluation, the soil dynamic propertiesresulted from triaxial test and strong-motion earthquake observation data, take thecoastal soft soil of Tianjin into analyzing. The coastal soft soil of Tianjin can dividinto limnetic facies soft soil, alluvium soft soil, marine soft soil and artificialreclaimed soil by topsoil category. This paper choosed the representative sites ofTianjin coastal soft soil to analyze seismic response with different methods referredabove, analyzed and compared the methods reflect the similarities and differences anddrawed a general conclusion.Then basing on analysis results reason out someconclusions which fits other coastal soft soil.It can be as a basis for practicalengineering seismic calculation of coastal soft soil.(1) This paper collects and analyses earthquake site response analysis methods ofdomestic and overseas related recent years.It can be as the reasons toanalyseearthquake site response with equivalent linear and non-linear methods.(2) Then we analyze and compare the soil dynamic constitutive model on principle.The result demonstates that the hyperbolic model is the better choice of fittingnonlinear parameters.(3) We choose the representative sites and collect the soil physical parameters and thetriaxial test data.Then we make use of the data to create four earthquake site response models: Tianjin culture center site model, International ConventionCenter site model, Xiangluowan site model and Yujiabao site model.(4) We pick those soil layers out which appear in the four site models referred aboveto create a new theoretical site model. Fitting soil dynamic property parameter inthe theoretical site model use MR, MRD and CD fitting methods respectively.Then we compare the results to draw a conclusion that MRD is the better fittingmethod.(5) Then we can get eight seismic waves of different peak value artificially by usingproportional method for Loma Gilroy seismic waves. Taking these data intoseismic site model, we need calculate thirty-two species of conditions withFLUSH which si equivalent linear calculation procedure and DEEPSOIL which isnon-linear calculation procedure. We get the conclusion after analyzing thesurface reaction peak acceleration, the surface acceleration response spectrumand eigenperiod.