沉积相和深度对第四纪土动剪切模量和阻尼比的影响

依据苏州第四纪地层特点,使用GCTS循环三轴试验仪对取自典型钻孔剖面100 m以浅的40个原状土样进行了剪应变10~(-5)~10~(-2)量级的动剪切模量和阻尼比试验,研究了土的沉积环境、深度和土类对土体的规准化动剪切模量比G/G_(max)和阻尼比λ的影响。当剪应变g1×10~(-4)时,G/G_(max)折减很小,土体处于非线性弹性状态。沉积相、土层深度和土类对苏州第四纪地层土的G/G_(max),l与g关系曲线的影响有明显差异。相同沉积相的同类土,土层深度越深,G/G_(max)随g增长而衰退越慢,l越小;深度相近的同类土,滨海相土比河泛相土具有更为明显的非线性,而滨海相土的l略高于河泛相土。沉积相相同、深度相近时,粉砂、粉质黏土、黏土的G/G_(max)随g增长而衰退的速率依次减慢;应变水平相同时,粉砂的l最小,粉质黏土的次之,黏土的最大。

Influence of sedimentary facies and depth on normalized dynamic shear modulus and damping ratio of quaternary soils

To contribute to a better fundamental understanding of the deformation behavior for Suzhou quaternary sedimentary soils, using GCTS cylinder apparatus cyclic loading testing system, a total of 40 cyclic triaxial tests are performed on various kinds of undisturbed soils at depth less than 100 m corresponding to a wide strain range in the order of 10^-5 to 10^-2. It is revealed that the variation characteristics of the normalized dynamic shear modulus (G/G_max) and damping ratio (λ) with the increasing shear strain (γ) are strongly influenced by the sedimentary facies, depths and types of soils. The reduction of G/G_max with the increasing values of γ when γ <10^-4 is small, and the soils show nonlinear elasticity. Under the identical conditions, the test results demonstrate that the increasing depth shifts the values of G/G_max and the relationship between λ and γ. Moreover, the sediments of flooded plain facies are more linear and have slightly smaller values of λ with the increasing values of γ than the sediments of littoral facies. Under the same sedimentary facies and similar depth, the reduction rates of G/G_max with the increasing values of γ for silty sand, silty clay and clay have a descending order, and the values of λ under the same γ for silty sand, silty clay and clay increase successively.