黄土初始结构性对其压缩屈服的影响

Effect of initial structural property of loess on its compressive yield

黄土是一种典型的具有结构强度的欠压密土,其特殊的结构性会使黄土的压缩曲线出现类似超固结土的明显转折点(对应的压力称为结构压缩屈服应力)。为分析黄土的初始结构性对其压缩屈服的影响,对6个场地的黄土进行了侧限压缩试验及单轴抗压强度试验,分别得到了各个场地不同含水率黄土的压缩屈服应力和构度指标。研究表明:黄土的构度指标与压缩屈服应力均随含水率的增大而减小,同时随含水率的增大,构度变化幅度小的黄土,其压缩屈服应力变化幅度也小;沉积时代相同的黄土,构度越大,其压缩屈服应力越大,两者呈线性关系;黄土的沉积时代不同,其构度与压缩屈服应力的线性关系就不同。分别给出了Q_3、Q_2黄土的构度与压缩屈服应力的线性关系式,并通过实例初步验证了此线性关系的适用性,为以构度为桥梁,利用简便易得的物理指标计算压缩屈服应力提供了一种途径。

Loess is a typical unconsolidated soil with structural strength. Its special structure results in an obvious turning point（where the pressure is called the compressive yield stress of structure） on its compression curve, similar to the curve of over-consolidated soil. To analyze the effect of initial structure on compressive yield of loess, confined compression tests and uniaxial compression strength tests were conducted on loess soils from six sites. The compressive yield stress and the structure index of loess with different water contents were obtained respectively. The results show that the structure index and the compressive yield stress of loess decrease with the increasing of water content. Meanwhile, with the increasing of water content, the variation of structure and variation of compressive yield stress are small. With the same sedimentary period of loess, greater structure index results in greater compressive yield stress. However, the linear relationship between structure index and compressive yield stress is different for the loess in the different sedimentary periods. The expressions of such correlations for Q3（late pleistocene） loess and Q2（middle pleistocene） loess are given respectively. Furthermore, the applicability of the correlations is verified by examples. Taking the structure as a bridge, there is a way to calculate compressive yield stress by using simple and easily available physical indexes.