液化循环流动土体动剪切特性试验研究

循环流动特性是剪胀性砂土液化变形的典型特征，为研究液化循环流动土体的动力剪切特性，在骨架相对密实度分别为35%、50%和80%的砂土中添加不同含量的细颗粒，以改变液化流动土体的重度，通过循环扭剪试验研究不同骨架密度、具有不同细粒含量的液化流动土体在大变形阶段的剪切模量及阻尼比的变化规律。试验结果表明：液化循环流动土体在流动大变形阶段仍具有一定的模量，模量随着应变的增大而逐渐减小；流动变形阶段的模量大小与液化土体的重度基本无关；强度恢复阶段模量与细粒含量及骨架相对密实度密切相关；液化大变形阶段卸载模量趋于稳定，其稳定值约为初始卸载模量的35%；阻尼比随剪应变的增大而先增大，当土体达到初始液化以后，阻尼比随剪应变的发展呈减小的变化趋势；对于相同骨架密度的土体，相变角随着细粒含量的增加而减小，临界状态线的斜率随着细粒含量的而增加而增大。

Experimental research on dynamic shear characteristics of #br# liquefaction circulating flow soil

Circulating flow characteristics are typical characteristics of dilatant sands in liquefaction stage. In order to study the dynamic shear behavior of liquefied circulating soils, fine particles of different contents were added to sandy soils with skeleton relative densities of 35%, 50% and 80% respectively, for the purpose of changing the gravity of liquefied flowing soils. The variations of shear modulus and damping ratio of liquefied flowing soils with different skeleton densities and different contents of fines in large deformation stage were studied by cyclic torsional shear test. The test results show that the liquefaction circulating flow soil still has a certain modulus in the stage of large deformation, and the modulus decreases gradually with the increase of strain; the modulus at the stage of flow deformation is basically independent of the weight of liquefied soils; the modulus at the stage of strength recovery is closely related to the content of fines and the relative density of skeleton; the unloading modulus at the stage of large liquefaction deformation tends to be stable, and its stability value is about 35% of the initial unloading modulus; damping ratio increases first with the increase of shear strain, and decreases with the development of shear strain when soil reaches initial liquefaction. For soils with the same skeleton density, the phase transition angle decreases with the increase of the content of fines, and the slope of critical state line increases with the increase of the content of fines.