Study On Dynamic Characteristics And Constitutive Model Of Xi’an Loess

Analysis of dynamic characteristics and stability of soil under a dynamic load are significant in the area of Anti-seismic analysis. Dynamic shear modulus and damping ratio are important basis for seismic analysis and design. Dynamic constitutive relation is a basic condition for dynamic analysis of soil. However, the empirical studies on dynamic characteristics and dynamic constitutive relation of unsaturated loess are still few at present. In that way, the study of the dynamics properties and the constitutive model of loess possess both theoretical and practical significance.The relationship between dynamic stress and dynamic strain, the dynamic shear modulus and the damping ratio are analyzed under different water content, different dry density, different frequency of dynamic load, different consolidation stress ratio and different confining pressure by dynamic triaxial tests. The research indicates that the curves of dynamic stress and dynamic strain is the hyperbolic model. Under the same test conditions,the dynamic stress with the same dynamic strain is larger when the water content is lower, this relationship is opposite for dry density, frequency of dynamic load, consolidation stress ratio and confining pressure. The dynamic shear modulus decreases and becomes stable with the increasing of dynamic shear strain. The maximum dynamic shear modulus is larger when the water content is lower, this relationship is opposite for dry density, frequency of dynamic load, consolidation stress ratio and confining pressure. The damping ratio of loess is the upward trend with the increasing of the dynamic shear strain and most of the values of damping ratio of loess fluctuate within the range of 0.1 to 0.32. Growth rate of damping ratio increased significantly with frequency increased when shear strain fluctuate between 0 and 0.3%.New dynamic constitutive model is created by theoretical derivation, which comes from the study on dynamic characteristics of loess. The variation of the model parameters is analyzed depending on the different experimental conditions, and the dynamic constitutive model is examined by test data. The research indicates that it reflects the relationship between dynamic stress and dynamic strain of loess well when shear strain is between 0 and 1%.