Soil erosion problems present a major threat to the nation's infrastructure. These problems include but are not limited to bridge scour, levee overtopping, meander migration, dams' internal erosion, and embankments surface erosion. This research addresses two aspects of soil erosion. The first deals with quantifying soils erodibility while the second deals with the problem of bridge scour. Many laboratory and, more recently, field tests have been proposed to measure soils erodibility. The first contribution of this research is a new in-situ erosion test, the Borehole Erosion Test (BET). This test consists of measuring the increase in the borehole diameter as a function of time for a given flow velocity during wet rotary drilling. The BET results in a soil erodibility profile along the entire depth of the borehole. BET tests are performed in clay and sand at the National Geotechnical Experimentation Sites at Texas A&M University. Computational Fluid Dynamics (CFD) simulations of the BET are conducted to determine the shear stress fields during the test. The experimental and numerical data are then used to compare soil erodibility results from the BET tests to those from the Erosion Function Apparatus (EFA) tests on soil samples extracted from the same borehole. Soil erosion problems present a major threat to the nation's infrastructure. These problems include but are not limited to bridge scour, levee overtopping, meander migration, dams' internal erosion, and embankments surface erosion. This research addresses two aspects of soil erosion. The first deals with quantifying soils erodibility while the second deals with the problem of bridge scour. Many laboratory and, more recently, field tests have been proposed to measure soils erodibility. The first contribution of this research is a new in-situ erosion test, the Borehole Erosion Test (BET). This test consists of measuring the increase in the borehole diameter as a function of time for a given flow velocity during wet rotary drilling. The BET results in a soil erodibility profile along the entire depth of the borehole. BET tests are performed in clay and sand at the National Geotechnical Experimentation Sites at Texas A&M University. Computational Fluid Dynamics (CFD) simulations of the BET are conducted to determine the shear stress fields during the test. The experimental and numerical data are then used to compare soil erodibility results from the BET tests to those from the Erosion Function Apparatus (EFA) tests on soil samples extracted from the same borehole. Bridge scour is the erosion of riverbed soils around bridge foundations at piers and abutments. Existing guidelines for maximum allowable scour are based on foundations stability criteria. An additional criterion must be considered when limiting scour depths at spill-through abutments where scour can cause slope stability failure of the embankment well before reaching the depth endangering the foundations. The second contribution of this research consists of equations and guidelines for determining the maximum allowable scour depth at or near spill-through abutments. These guidelines are based on a combination of a review of the existing knowledge, DOT survey, analyses of different scour failure scenarios, slope stability simulations, and a study of case histories. They can be easily followed by bridge inspectors to judge the criticality of the measured or observed total scour at the abutments, including both contraction and local abutment scour.
