MEASUREMENTS OF WATERDROP IMPACTS (EROSION, SOIL)
Abstract
This thesis develops a load function for vertical waterdrop impact stresses on soil surfaces and shows that the load induced on a soil surface is material dependent. Impact forces were measured on 3.31, 3.83, and 4.51-mm diam drops falling from heights of 0.5, 1.4, 3.3, 6.4, and 14.0 m, and for 5.25-mm diam drops from 14 m onto piezoelectric transducers. Peak forces occurred within 13 to 21 (mu)s of contact, ranged from 1.0 to 3.8 N, and decreased to 0.5 N after 100 (mu)s. Average pressures decreased to 100 kPa after 50 (mu)s. Peak force was determined to be a function of either drop kinetic energy or momentum for individual drop heights, but the relationship varied with different heights. Peak force was proportional to diam squared times velocity cubed for all drop sizes and fall heights. A non-dimensional representation of force vs. time duration of impact curves was determined. Pressures of impact of waterdrops on soil surfaces were measured with a 1-mm diam piezoelectric transducer and a 5.6-mm diam waterdrop with a height of fall of 14 m. Two soils at two bulk densities and two matric potentials were used. Average peak impact pressures were greatest in the range of 1.8 to 2.3 mm from the center of impact and they were 190 to 290 kPa. These stresses were almost two orders of magnitude less than those for rigid surfaces. Vertical waterdrop impact stress on soils was presented as a function of area and time during impact.
Degree
Ph.D.
Subject Area
Civil engineering
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