Dynamic characteristics of saturated loess under different confining pressures: a microscopic analysis

To explore the influence of confining pressure on the dynamic characteristics of saturated loess and variation of the characteristics in micro-mechanisms therein, dynamic triaxial testing of loess from Xianyang was carried out. The dynamic elastic modulus of saturated loess after different numbers of cycles was available through the test and the relationship between the dynamic elastic modulus and confining pressure can be analysed. A scanning electron microscope (SEM) examination was conducted to assess the microstructural characteristics of the specimens. From both qualitative and quantitative aspects, the variations in microstructure were analysed. The microstructural parameters which had greater correlation with macroscopic strength were found based on grey relationship theory, then the relationship between them was found by curve-fitting. The results show that, the dynamic elastic modulus of saturated loess was increased as the confining pressure increases, but decreased with increasing vibration cycle and tended to be stable over time. The approximate microstructural parameters selected were correlated to the dynamic elastic modulus in addition to the average pore shape factor; because of the high correlation with the dynamic elastic modulus, the average diameter of the pores, the average shape factor and fractal dimension of the morphology of structural units were selected to fit the dynamic elastic modulus.