Erosion Rate of Compacted NA‐Montmorillonite Soils

Erosion rates of unsaturated compacted Na‐montmorillonite clays are measured under a range of tractive stresses from surface flows in a rectangular flume. The degree of saturation of compacted samples ranges from 0.52–0.97. The Na‐montmorillonite (Volclay bentonite) is mixed with ground silica to obtain samples with various percentages of clay. Samples of 100, 70, 40, and 10% clay content by dry weight are tested. Samples are compacted under 700 Pa into sample containers with 160‐cm2 surface area and are subjected to flowing water in the flume. The results of the study show that the erosion rate of Na‐montmorillonite soil samples increases when clay content decreases and is independent of compaction water content. The relationship between erosion rate and tractive stress is linear for all Na‐montmorillonite samples. For the range of water content tested, an empirical relationship is developed to estimate the erosion rate of compacted Na‐montmorillonite clays as a function of percent clay content and tractive stress.