A new technique for rapid measurement of continuous soil moisture characteristic curves

The soil moisture characteristic (SMC) curve of a soil describes the relationship between the soil suction (tension in the soil pore water) and its water content. The majority of traditional methods used to obtain SMC curves involve gathering individual point measurements of soil water content over a range of applied soil suctions, and then fitting a curve through these points. Each point measurement requires at least a day of testing to gather, leading to a total testing time of weeks to assemble the whole SMC curve. This paper presents a technique to obtain a complete, continuous SMC curve in a total preparation and testing time of 3–5 days. During evaporative drying of the soil specimen under examination, a digital laboratory balance and a high-capacity tensiometer, both connected to a data acquisition system, monitor continuous pore water loss and suction data respectively. The tensiometer is composed of a pressure transducer for suction measurement and an extremely fine porous ceramic that interfaces between the specimen and the transducer. To date, the technique has been successfully applied to resedimented, non-clay soils. Experimental results from the new method are in agreement with results from capillary fall tests. The paper also provides some insight into tensiometer behaviour and features of SMC curves.