ON THE DETERMINATION OF THE SOIL-WATER CHARACTERISTIC CURVE USING THE PRESSURE PLATE EXTRATOR

摘要

The pressure plate extractor is commonly used to measure the soil water characteristic curve (SWCC). In the measurement, two methods are adopted to determine the soil water content, through weighing the soil sample and the outflow, respectively. With the first method, part of soil mass may lose during the operation, while with the second method air bubbles may accumulate under the ceramic plate, inducing the air-water interfacial effect. All these factors may result in error in the measurement. To resolve these issues, a modified method for weighing the outflow is introduced. By comparing the data obtained with theses three methods, it is found that the method of weighing soil is suited for the case when matric suction is large or testing time is long, whereas the method of weighing outflow is suitable only when matric suction is small and testing time is short. It is also found that the proposed adjusted method of weighing outflow can be effectively used to determine the soil water characteristics for all soils.