红黏土的土水特性及其孔隙分布

以桂林红黏土为研究对象,采用压力板法、滤纸法和饱和盐溶液蒸气平衡法3种方法研究在全吸力范围内原状样和压实样的土水特性,并结合压汞试验研究其孔隙分布。试验结果表明:当吸力约小于10 MPa时原状样的土水特征曲线略低于压实样,主要原因是原状样内部裂隙随吸力的增加而不断发展;当吸力约大于10 MPa时两者的土水特征曲线几乎重合。原状和压实桂林红黏土样的土水特征曲线与典型的土水特征曲线不同,即在过渡段均不是单一直线。此外,原状样为单峰孔隙结构,压实样则为双峰孔隙结构,原状样的最终收缩变形量比压实样大。不同干密度的压实样内部颗粒间孔隙分布几乎相同,而积聚体间孔隙或积聚体内孔隙相对较大孔隙存在差异;由此可解释在高吸力范围内不同干密度压实样的含水率与吸力关系土水特征曲线几乎重合;以饱和度与吸力关系表示时,干密度越大,土水特征曲线越高。

Soil-water characteristics and pore-size distribution of lateritic clay

The pressure plate method, filter paper method and vapor equilibrium technique with saturated salt solution and mercury intrusion porosimetry tests on Guilin lateritic clay are used to investigate the soil-water characteristics and pore-size distribution of undisturbed and compacted specimens in full suction range. The test results show that the undisturbed specimen has lower water content and saturation degree than the compacted one in the suction ranging from 0 kPa to 10 MPa because of the development of internal crack of undisturbed specimen with the increasing suction. When the suction is higher than 10 MPa, the soil-water characteristic curves (SWCC) coincide with each other. In the transition zone, the SWCCs of the undisturbed and compacted specimens are different from the typical ones. The undisturbed natural specimens exhibit a unimodal pore-size distribution, and the compacted ones usually have a double-porosity microstructure. The stability of shrinkage of the undisturbed natural specimen is larger than that of the compacted one. The compacted specimens with different dry densities also have the same pore-size distribution between particles, while the inter-aggregate pore distribution differ between the compacted specimens with different dry densities. It explains that when it is expressed by the relation between suction and water content, the SWCC is independent of dry density in the high suction range. When it is expressed by the relation between suction and saturation degree, the SWCC with high dry density is higher than that with the small one.