Abstract: The combination of weathered sand and expansive soil as a subgrade has the advantages of simple operation process, environmental friendliness and low cost. The law of influence of confining pressure and vibration frequency on dynamic characteristics such as dynamic strength, dynamic elastic modulus and equivalent damping ratio of weathered sand improved expansive soil is studied by GDS dynamic triaxial test. The results show that: The stress-strain backbone curve and the damping ratio and strain relationship of the modified expansive soil improved by weathered sand can be described by hyperbolic function; with the increase of dynamic strain, the dynamic elastic modulus of the modified expansive soil decreases, the damping ratio increases; Under the recycle action, the stress-strain relationship curve of the modified expansive soil in weathered sand is closed hysteresis loop. The axis of the hysteresis curve increases with the increase of the dynamic stress and the slope decreases. The soil sample exhibits typical strain softening characteristics. With the confining pressure and the loading frequency increases, the dynamic elastic modulus of the expansive soil is increased, and the damping ratio is decreased. The effect of the frequency on the dynamic elastic mode is concentrated in the range of strain εd less than 0.2%, and the influence on the damping ratio is concentrated in the range of εd less than 0.1%.

Key words: weathered sand, expansive soil, dynamic strength, dynamic elastic modulus, equivalent damping ratio