ANALYSIS FOR EFFECT OF MICROSTRUCTURE ON SWCC OF COMPACTED LOESS

Soil water characteristic curve(SWCC) is a basic physical-mechanical relation of unsaturated soils and changes the physical index of water content to the mechanical index of forces among soil particles. Soil water characteristic curve is controlled by soil structures. To investigate the effect of soil structure on the SWCC, the compacted loess samples are made with three different moisture contents in the study. They are less than the optimum 8%, at the optimum 17%, and more than the optimum 19%. Mercury intrusion poroimetry(MIP) and scanning electronic method(SEM)as well as filter paper method are respectively used to explore the pore size distribution(PSD), the soil water characteristics(SWCC) and the microstructure of the compacted loess at difference water contents. It can be observed from the SWCCs and PSds that compacted loess at different moisture contents have a significant impact on the microstructure and soil water characteristics. In low suction zone, the SWCCs of three compacted loess are significantly different. The SWCC of dry of optimum is the steepest. It tends to be the same in the high suction region. The PSD varies greatly in the macro-pores and is almost the same in the micro-pores, which is similar to the SWCC. By comparing the SWCC and PSD, it is found that the pore distribution of loess compacted with different moisture content is tightly related to SWCC. The larger the pore size density, the steeper slope of SWCC. SEM imagines also show the typical characters of the three compacted soils as follows:(1)the specimen with the less optimum moisture content is dominated with large inter-particle pores; (2)the specimen with more than the optimum moisture content is dominated with smaller inter-particle pores; and (3)the specimen at the optimum has a wide range of pore distribution.