THE STUDY OF THE SPLASH AND SOIL DETACHMENT FROM SINGLE WATERDROP IMPACT
Abstract
The purpose of this project was to study soil detachability and the splash mechanism from single raindrop impact. A simple relationship that predicts soil detachment was tested for nine soils and three drop sizes. This relationship expressed splash weight of soil as a linear function of the ratio of raindrop kinetic energy to soil resistance expressed as the undrained shear strength. An improved and inexpensive raindrop tower 8.9 m in height was designed so that a single drop will hit a soil target area 1.6 cm in diameter. For the soils used in this study, clay content ranged from 3.4 to 52.5 percent, organic matter from 1.0 to 4.6 percent, CEC from 9.1 to 28.7 meq/100g, and surface area from 21 to 202 m('2)/gm. The surface shear strength for each soil was altered by remolding the soil to three bulk densities and by equilibrating the soil cores to matric potentials of -5, -19, -38 and -62 mbars. The weight of soil detached from the impact of single waterdrops 3.0, 4.6 and 5.6 mm in diameter was closely correlated with the undrained soil shear strength as measured by the Swedish fall cone device. The coefficient of determination values between splash weight and the force-resistance ratio for individual soils were high (r('2) = 0.88 to 0.97); however, the coefficient of determination among all soils was lower (r('2) = 0.81). A maximum coefficient of determination of 0.61 was found when soil properties other than shear strength were used as independent variables to predict soil splash. From the results of high speed photography and from soil mechanics principles, a new concept for describing the mechanism of soil detachment from raindrops impacting on saturated soil surfaces was proposed. The impulsive loading caused by the impacting drop does not permit time for drainage; thus there is no change in total soil volume under the impulsive load application of the drop; however, the vertical force of the drop is transformed to lateral shear caused by radial flow of the impacting drop. Splash angle is determined by the depth of the cavity and the size of the bulge surrounding it. Splash angle was highly correlated with the soil shear strength.
Degree
Ph.D.
Subject Area
Agronomy
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.