EXPERIMENTAL STUDY ON CHARACTERISTICS OF PORE WATER DISTRIBUTION AND WATER-HOLDING CAPACITY OF SOIL

The soil water characteristic curves of sand, silty clay and clay are measured by axis translation technique. The T₂ distribution curve of specimens are tested under different matric suction loading steps combining with nuclear magnetic resonance(NMR) technique. The distribution of pore water in soil is discussed with the T₂ distribution curve from the microscopic point of view during drying process. The results show that volumetric water content gradually reduces with the increase of the suction. The drying curve can be divided into three sections:boundary effect zone, transition zone and residual zone. In addition, the clay water-holding capacity is obviously higher than that of silt and sand. The tests of NMR are corresponded with drying process in the pressure plate apparatus. The results of NMR tests further show the drainage process of soil from the microscopic of perspective. On the whole, the large pore water with large potential energy is discharged first in the drainage process of soil, and then the water in small pores begins to drain. However, this rule is not absolute, because of the complexity of the soil pore structure. There will be a phenomenon of simultaneous discharge of different size porosity of pore water and the redistribution of pore water in soil occurred during the drying process.