Experimental Study On Dynamic Characteristics Of Loess Considering Microstructure

Loess is a special kind of Quaternary sediment with porous and weak cementation,and its macro-mechanical properties are controlled by internal structures.Its mechanical property which is different from other soils is determined by the special structure of the loess.Therefore,based on the previous research on the structural research of soil,the electronic scanning electron microscope(SEM)test and dynamic triaxial test was carried out in this paper,and a new method for quantitative extraction of loess microstructure parameters is proposed.The variation of loess microstructure with time and space is summaried.And above all,we make a deep research on the structural parameters of the soil and establishe the relationship between micro parameters and macro parameters.Finally,the structural parameters are introduced into the hyperbolic model,and modifies the dynamic constitutive model of loess.The main results are:1.Based on the characteristics of loess microstructure image,using the software matlab and IPP to pre-process and segment the image,the microstructure parameters can be measured more accurately.2.The microstructures of loess in different areas(Xining,Yongdeng,Lanzhou,Xiji and Ruicheng)were observed by electron scanning electron microscopy(SEM)and find that the microstructure of loess is closely related to region,depth and climatic conditions.The arrangement of particles and pore structure of the original loess is relatively random and its probability entropy is between 0.927 and 0.9090.From the northwest to the southeast direction,the content of large gap gradually increases,the pore surface becomes rough,and the fractal dimension has an increasing trend.3.Based on dynamic triaxial tests on intact loess and man-made loess which have the same dry density of Yongdeng,Xiji,and Ruicheng under different moisture and different confining pressures,the stress-strain dynamic constitutive relationship of the tow kind of loess show hyperbolic model.The structural parameter which can reflect not only arrangement of the particaes but also cementing power were obtained in this paper and also we established a quantitative relationship with dynamic strain,moisture content and confining pressure.4.Grey Incidence Function was applied to analyse relationship between structural parameter and the variation of microstructure parameters.It is concluded that the porosity,probability entropy,equivalent diameter and fractal dimension have strong correlation with structural parameter;Structural stress strain curve is found in the elliptic by introducting the structural parameters to the dynamic stress strain curves of undisturbed loess.Using the method we can fiind that test value of the constitutive relation agree with the theoretical value and can better simulate the deformation characteristics and the mechanical characteristics under dynamic loading.