Study On Dynamic Behaviors Of Unsaturated Loess In Different Vibration Frequencies

Loess is widely distributed in Midwestern China, project constructions are becoming more and more in loess regions. Presently, most researches of the loess'dynamic behaviors are focus on the influence of water content or consolitation ratio in a certain vibration frequency. But the research in a certain vibration frequency is far from the demand of project practic, the dynamic behaviors of the loess should be different if the vibration frequency changes. So the influence of vibration frequencies on dynamic behaviors of loess should be researched.In this paper, the experiment of unsaturated loess samples is completed in different vibration frequencies, different consolidtion pressures, different water content based on torsion shear apparatus, the influence of vibration frequencies on dynamic constitutive relation, dynamic shear modulus,damping ratio,dynamic structural strength, vibrating subsidence are mainly studied. The shear failure of compacted loess in different frequencies are studied based on torsion shear apparatus, the effecting law of frequency on dynamic strength and dynamic strength parameter is mainly researched. The research results are:1. All of theτd~γd constitutive curves of intact loess and remodeling loess assume a hyperbolic model in different vibration frequency, the intact loess show the law more clear than the remodeling loess.2. In certain defined water content and confining pressure, the maximum dynamic shear modulus increased with the increasing of vibration frequencies; In certain defined vibration frequency and confining pressure, the maximum dynamic shear modulus decreased with the increasing of water content; In certain defined water content and vibration frequency, the maximum dynamic shear modulus increased with the increasing of confining pressure.3. The relation between damping ratio and vibration frequencies is not clear, most of the damping ratios of intact loess is 0.20 to 0.40, and most of the damping ratios of remodeling loess is 0.15 to 0.35.4. Under the condition of low water content, the intact-remodeling stress differences of unsaturated loess show a peak value, then decreased and tend to be stable. Under the condition of high water content, the intact-remodeling stress differences of unsaturated loess increased with the increasing of dynamic shear strain, it will be stable when the dynamic shear strain achieved 1%. Under the condition of same water content and confining pressure, the dynamic shear strength increasing with the increase of vibration frequencies.5. Under the condition of same vibration frequency, confining pressure and dynamic shear strength, the vibrating subsidence of unsaturated loess is increasing with the increase of water content. The influence of vibration frequency on vibrating subsidence of unsaturated loess is not clear; the vibrating subsidence of unsaturated loess is determined by water content and dynamic shear strain. 6. In certain defined confining pressure, the dynamic strength of compacted loess is increased with the increasing of vibration frequencies, shows a positive relation with vibration frequencies. Both of the dynamic cohesion (cd ) and the internal fraction angle (φd) of the compacted loess are increased with the increasing of vibration frequencies. The dynamic cohesion and the internal fraction angle are decreased and tend to be stable with the increasing of the vibration frequencies, both of the dynamic strength parameters can be fitted with logarithm curve.