季冻区典型土类动剪切模量阻尼比计算方法

采用专门设计的低温共振柱仪进行试验研究,研究典型土类动剪切模量阻尼比随负温的变化规律及计算方法。提出温度影响系数的概念,并以较为符合实际的固结压力和冻结过程,完成了黏土、粉土与砂土在常温及不同负温下的动力试验,给出了这3种典型土类不同负温下初始剪切模量、剪切模量比和阻尼比的计算公式。结果表明:无论何种土类,负温对其初始剪切模量、剪切模量比和阻尼比都有重要影响,相应的温度修正系数按Boltzmann与指数函数变化,均在0℃到-6.0℃快速变化之后趋于平缓,但变化程度和修正公式中的参数均与土类有关;随温度降低,3种土类初始剪切模量增长十分显著,完全冻结黏土、粉土和砂土分别为常温土初始模量的50倍、25倍和13倍;随温度降低,3种土类参考剪应变降低十分显著,但完全冻结后3种土的动剪切模量降低程度接近;随温度下降,3种土类最大阻尼比均显著减小,完全冻结后的黏土最大阻尼比降幅最大,砂土降幅最小,粉土居中。3种典型土类负温下动剪切模量阻尼比修正公式,其反映的现象和规律与国际上近期成果定性相符。

Method for dynamic shear moduli and damping ratio of typical soils in seasonal frozen region

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.