Method for dynamic shear moduli and damping ratio of typical soils in seasonal frozen region
摘要
Using specially designed low-temperature resonant column apparatus, change rules of dynamic shear moduli and damping ratio with negative temperature and their computational methods for three soils are investigated. Concepts of temperature correction coeffecient are proposed, and dynamic tests on clayey, silty and sandy soils under room and negative temperatures are conducted based on actual consolidation pressure and freezing process. The formulae under different negative temperatures for the initial shear modulus, shear modulus and damping ratio of the soils are also proposed. The results indicate that, for each type of soil, the negative temperature has significant impact on the initial shear modulus, shear modulus and damping ratio, while the corresponding temperature correction coefficient changes according to the combinatorial functions of Boltzmann and exponent. The change becomes gentle after rapid change from 0℃ to -6℃, and the degree of change and parameters fitting the functions are related to soil type. With the decrease in temperature, the initial moduli of three soil types increase very significantly. The completely frozen samples of clayey, silty and sandy soils gain 50, 25 and 13 times the initial shear modulus at room temperature respectively. The reference shear strain remarkably falls with the deceasing temperature, and all these soil dynamic shear moduli have simultaneous attenuation after completely frozen. The maximum damping ratio of the 3 soil types decreases distinctly at the lowering temperature, and to the magnitude of decreasing, the sand is the minimum, the clay is the maximum, and the silt is the intermediate. The proposed correction formulae for dynamic shear moduli and damping ratio of 3 typical soils are qualitatively consistent with recent achievements in the world on the physical laws and phenomena.