The Capillary Rise in Fine and Coarse-Grained Soils Considering the Matric Suction

Few pieces of research have been conducted on the phenomenon of capillary rise in the field of soil for agriculture and geotechnical engineering. The rate of capillary rise of water in fine and granular soil is one of the major challenges for rising experiments in vertical open-tubes, as the time required for the water to reach the maximum height of capillary rise (hc) can vary from 50 to 400 days. The control variables during the capillary experiment are mainly: saturated and unsaturated hydraulic conductivity, soil density, water content, soil column height, and velocity of capillary rise. Thus, this paper presents theoretical and experimental studies of capillary rise in several soils based on matric suction models. Results were gathered by comparing the behavior of capillary rise using the analytical solutions developed by Lu (2016), Lu and Likos (2004), and by Terzaghi (1943). On analysis of the results, it was concluded that the equation proposed by Lu and Likos (2004) is the most suitable to predict the capillary rise velocity for the fine-coarse soils and the equation proposed by Lu (2016) is more suitable to predict the matric suction. Other mathematical model developed by Liu et al. (2014) is also suitable to estimate the hc but don’t consider the velocity of the water. The capillary rise method to measure the matric suction must be more applicable in sandy soil than clayey soils.