Study On Dynamic Characteristics Of Three Kinds Of Special Soils

Soil dynamics and seismic response have received much attention in the field of geotechnical engineering.It is one of the important contents and hot issues of seismic design of geotechnical engineering,Because of its special material composition,forming environment,and structure,special soils usually display different engineering and dynamic properties from ordinary soils.China is one of the countries with the worst earthquake disaster in the world.Therefore,it is of great significance to study the dynamic characteristics of special soils for engineering construction and disaster prevention work in special soil areas.Based on the previous studies,in this paper,three kinds of special soils,soft soil,loess and laterite,are studied.At the same time,a database of physical and mechanical parameters of these three kinds of special soils is established.Based on the relevant data of this database,systematic research work is carried out on engineering characteristics,dynamic characteristics and seismic response characteristics of these special soils.The main research work and the results obtained are summarized as follows,1.The research status of special soil dynamics is reviewed.Based on the previous studies,the relevant research conclusions of three kinds of special soils dynamic properties and engineering characteristics at home and abroad are summarized,and the research progress of engineering,dynamic and seismic response characteristics of special soil is reviewed.On this basis,the problems existing in this research field are briefly discussed and commented,and the research that needs to be carried out in the future is put forward.2.Based on the test and data collection,a database of these special soils physical and mechanical parameters is established.The physical and mechanical properties and dynamic parameters of three kinds of special soils in some parts of china are collected.On this basis,a database which includes the general physical and mechanical properties of three special soils,and the data of soil dynamic shear modulus ratio,damping ratio,and shear wave speed is established.The database is presented in the form of a web page,which can be remotely logged in,updated,and downloaded in the form of Excel.The database provides data support for the research of the engineering characteristics of three kinds of special soils.3.Based on the data of database,the physical and mechanical parameters of soft soil,loess and laterite are calculated,and the regression formulas are given,In this paper,the ranges of the physical and mechanical parameters of three special soils are given by statistics,and the relation between each parameter is established by scatter plots,correlation coefficients,and linearity tests(F test)of the fitting equation.On this basis,the correlation between the physical and mechanical parameters of the special soils is analyzed,and the engineering characteristics of three kinds of special soils are analyzed deeply.The relationship between the physical and mechanical parameters of the three kinds of special soils is established,which will provide convenience for the engineering4.Based on the test and collected data,the dynamic characteristics of three kinds of special soils are studied,and the dynamic parameters of these special soils in typical regions are given,and the changes of shear wave velocity with depth are calculated.Based on the test data and collected relevant data,the range values and average values of the dynamic parameters(e.g.dynamic shear modulus ratio,damping ratio,and shear wave velocity)of the three kinds of special soils in typical regions are statistically given.Through regression fitting method,the recommended values of these special soil dynamic parameters are given.Using dynamic triaxial tests,the effects of different test conditions on the dynamic shear modulus ratio and damping ratio of soft soil and loess are discussed.At the same time,based on the collected drilling data,an empirical formula of shear wave velocity of the soft soil,loess and laterite changing with buried depth obtained by SPSS(Statistical Product and Service Solutions)software.The rationality of formula is proved from the real sample;this work provides a reference for the analysis of seismic response of soil layers in soft soil,loess and red soil.5.Using the method of soil layer seismic response analysis,the differences of three kinds of special soil dynamic responses are compared,and the recommended values of these special soil dynamic response calculation parameters are given.In this paper,three special soil homogeneous single soil layer calculation models are established,and the SOILQUAKE soil layer seismic response analysis program is used for calculation and analysis.Based on the calculation results,the influence of the dynamic shear modulus ratios,damping ratio,shear wave velocity and ground motion on characteristic parameters of design response spectrum is discussed.In addition,on the basis of actual drilling data of typical areas,three soil layer calculation models of actual special soil sites are established,which are used to calculate the dynamic characteristics of the special soil are studied in terms of peak acceleration,design response spectrum shape and characteristic parameters.Based on the research results of this paper,the recommended values of dynamic shear modulus ratio,damping ratio,shear wave velocity and density of special soil are given.This work not only has important reference value for seismic design in soft soil,loess and laterite area,but also enriches the research results of soil dynamic parameters.