土结构性对天然软黏土压缩特性的影响

Effect of soil structure on compression behavior of natural soft clays

天然软黏土普遍受到土结构性的影响,明确结构性对软黏土压缩特性的影响机制显得尤为重要。对两个天然软黏土原状样进行室内一维固结试验,得到的压缩曲线与已有文献中搜集的39个原状样压缩曲线进行比较。压缩曲线在对数坐标下均呈现倒S形,并存在明显的结构屈服压力。采用双对数坐标处理后,压缩曲线可由双直线较好地表示,易于确定固结屈服压力。41个原状样屈服后的压缩指数和屈服点含水率之间的定量关系,与基于重塑土定量公式计算的压缩指数与固结屈服压力下重塑土含水率的定量关系相一致。对比结果表明:天然软黏土屈服后的压缩特性取决于屈服时的含水率,而与土结构性无关,解释了天然土压缩曲线位于重塑土上方是由于对应屈服点含水率不同而引起的。

Natural soft clays are generally subjected to the effects of soil structure. So evaluating the influence mechanism of soil structure on the compression behavior of soft clays is of utmost importance. One dimensional consolidation tests are performed on two natural soft undisturbed clays to obtain their compression curves, which are compared with the collected consolidation test data for 39 natural soft clay samples collected in literatures. It is observed that the compression curves under logarithmic coordinates show an inverse S-shape and obvious consolidation yield stress. The oedometer test data can be well represented by two straight lines under bi-logarithmic coordinates and the consolidation yield stress can be easily obtained. Relationships between compression index in the post-yield state and water content at yield point for total 41 clay samples can be well quantitatively presented, which is consistent with the quantitative relationships for remolded clay samples between compression index and corresponding water content at yield point. Comparison results show that the compression behavior of natural clays in the post-yield state is mainly controlled by the water content at yield state, which is independent of the resistance of soil structure. Compression curves for natural clay samples lies above the corresponding curves ofremolded samples can be explained as being induced by the difference in water contents.