应力水平对结构性软黏土静力和动力变形特性影响的试验研究

采用原状和重塑软黏土样进行测量剪切波速的压缩试验及循环三轴试验，结果表明：在静荷载作用下，原状软黏土的变形特性随应力水平变化均可分为3个阶段，这3个阶段以先期固结应力和结构届服应力为分界点，利用剪切波速可简单、方便地判定出这2个关键应力值；重塑软黏土的变形规律与应力水平无关。对土体施加循环荷载时，两种土在不同固结应力下的应变一振次关系曲线上均存在着一个转折点，施加的动应力幅值小同，转折点应变也不相同，但该应变与相应的破坏振次呈线性关系。对于原状软黏土样，其转折点应变破坏振次关系分3个阶段变化，且与压缩试验的3个阶段具有良好的对应关系；对于重塑软黏士样，其线性关系基本不随应力水平变化而变化：当原状土结构破坏后，两种土样的变形规律趋于一致。

EXPERIMENTAL STUDY ON INFLUENCES OF STATIC AND CYCLIC DEFORMATIONS ON STRUCTURAL SOFT CLAY WITH STRESS LEVEL

This paper presents the results of an experimental investigation performed to study the influences of static and cyclic deformations on undisturbed and remolded soft clay sampling. The tests indicate that the deformation of undisturbed soft clay changing with stress level could be divided into three stages. The preconsolidation and structural yielding stress are the cut-off point of these three stages and they could be determined by shear wave velocity measurement. The deformation characteristic of remolded clay is almost independent of stress level. When carrying out cyclic triaxial tests, the strain curves with cycle number of natural and remolded soft clay have all turning points under different amplitudes of stress. Before the turning points appear, the strain develops slowly and keeps to a small level. But after the turning points appear, the strain develops quickly and becomes large finally. The strain at turning points changed with different stress amplitudes, but they almost fail on a same line and could be fitted by a linear equation. The change of fitting parameters of natural soft clay could also be divided into three stages which correspond well to consolidation tests. And similarly, the fitting parameters of remolded soft clay almost did not change with stress level. The deformation characteristic of these two kinds of soft clays tends to be consistent when the structure of natural soft clay is damaged.