A Master of Science thesis in Civil Engineering by Rawan Ibrahim Aqel entitled, “The Use of Lime to Stabilize Clay Soil against Internal Erosion”, submitted in December 2018. Thesis advisor is Dr. Mousa Attom. Soft and hard copy available.
Internal erosion failure of soils in hydraulic structures is one of the most catastrophic failures in civil engineering projects. Therefore, it is vital to stabilize the soil against this phenomenon. Different materials and methods have been used to stabilize the soil in general such as cement, lime, fly ash, oil shale ash, burnt sludge and other solid wastes. The main objective of this study is to investigate the potential use of lime as a new stabilizing agent against internal erosion of cohesive soil. To achieve the goal of this research, two types of soils CH (Clay of High Plasticity) and ML (Low plastic silt) were selected and used. The selection of the cohesive soils was based on the physical properties of the soils such as gradation, clay content, silt content and Atterberg’s limits. The two types of soils were mixed with lime at different percentages; by the dry weight of the soils. Specimens were remolded at 95% of maximum dry density and optimum moisture content. Two identical specimens from each soil were prepared at 95% of maximum dry density and optimum water content with 0.0% lime as control specimens. The Hole Erosion Test was employed to test the remolded specimens at three different curing times namely; 1 day, 2 days, and 7 days from the time of preparation. The different erosion parameters of the soil such as the friction factor, critical shear stress, and the coefficient of soil erosion, were evaluated and used to calculate the Erosion Rate Index. It was found that lime is more effective when used with CH type soil than with ML type of soil. The addition of 2.0% of lime by the dry weight of the soil will stabilize the CH type of soil, while more than double this percentage is needed to stabilize the ML type of soil. The Erosion Rate Index increased up to 5.7 (very slow erosion rate) at 2.0% and 5.0% lime for CH and ML type of soil, respectively. Additionally, it was found that the increase in the percentages of lime increased the Critical Shear Stress significantly and an increase in curing time increased the Erosion Rate Index and improved the stabilization of both soils against internal erosion.