压实高岭土干燥收缩特性试验

为研究初始干密度和初始含水率对高岭土干燥收缩行为的影响，探究其干燥收缩机理，采用数字图像相关法来测量环刀试样的径向变形，在设计的干燥收缩试验平台进行了一系列干缩试验，结合试验得到的收缩曲线和相应的土水特征曲线获得吸应力固结曲线。结果表明:饱和高岭土大部分收缩变形发生在进气点之前的饱和状态；试样在干缩过程中以径向变形为主，表现出比较明显的各向异性，这种各向异性的变形特性随初始饱和度的增加而减弱；随着初始干密度增大，试样干燥收缩稳定所需要的时间逐渐减小，稳定时的体积变形也相应减小，然而试样的初始干密度和饱和度对收缩变形稳定时的含水率几乎没有影响；吸应力固结曲线与饱和土的等向固结曲线近似重合的曲线形态表明吸应力和净平均应力对土收缩变形的作用效果是一致的；在等向应力条件下，有效应力是影响土体干缩变形的决定性应力；提出的结合干燥收缩试验和等向固结试验曲线的间接测量土水特征曲线的方法是相对可靠的。

Experiment on Drying Shrinkage Characteristics of Compacted Kaolin

In order to study the effect of initial dry density and water content on the shrinkage behavior of Kaolin, and research the drying shrinkage mechanism, a series of drying shrinkage tests were carried out to measure the radial strain of the cutting specimen by digital image correlation method. The suction stress compression curve (SSCC) was proposed by combining the shrinkage curve and corresponding soil water characteristic curve (SSCC) of the soil. The test results show that most of the shrinkage deformation of saturated specimen occurs before the air-entry point while the soil is still fully saturated. The anisotropy of the shrinkage deformation of the specimen is evident as radial shrinkage strain is dominated upon drying, while the soil has a tendency to exhibit isotropic volume shrinkage behavior as water content increases. The volumetric shrinkage strain, as well as the elapsed time required for the drying process, decreases with the increase of the initial dry density. However, the water content of the specimen is the same at the end of the drying test, regardless of the initial dry density and water content. The comparison of the SSCC and saturated isotropic compression curve indicates that the suction stress and net mean stress have the same effect on the contraction deformation of the soil. It concludes that effective stress plays a decisive role on the volumetric shrinkage behavior when the soil is under isotropic condition. The proposed method by combining the shrinkage curve and corresponding isotropic compression curve to indirectly measure soil water characteristic curve is relative reliable.