Abstract: In order to improve test method of soil-water characteristic curve (SWCC), the pressure plate extractor is employed and drying tests are carried out on the basis of four cutting ring specimens and twelve triaxial specimens. The potential factors and abnormal phenomenon in the test are investigated. The results show that there are differences between the SWCC of specimens, even if the specimens are reconstituted at the same condition, and the differences have a direct relationship with the poor particle size distribution. There is the evaporation effect in the drying tests, and the water loss caused by evaporation is dominant with the increasing of time, so equilibrium condition should be adjusted on the basis of evaporation. The SWCC is obviously influenced by side protecting, especially to the specimen with big ratio of height to diameter, evaporation will become main factor of water loss without side protecting. The transverse crack which is an abnormal phenomenon in the specimen does not affect the result of SWCC, but it should be further investigated because the generation mechanism could show the shortage of axis translation technology. Based on the above conclusion and other test results, some suggestions and improving methods for SWCC test are proposed.

Key words: SWCC, pressure plate extractor, difference of specimen, evaporation effect, side protecting, crack