METHODS FOR MEASURING SOIL VELOCITIES CAUSED BY A SWEEP

A field experiment was conducted to measure surface soil velocity and to determine the relation between soil aggregate velocities at the too l surface and at the soil surface. A technique incorporating use of bo th a video camcorder and wood blocks was developed to measure surface soil velocity. Soil velocity direction at the tool surface was measure d from scratch marks on the tool. Velocity measurements were made for three sweeps with different rake angles operated at three speeds and t wo depths. Surface soil moved in either of two modes: V-flow (upward a nd laterally in the shape of one leg of the letter V) or snowplow (ini tially moving upward and subsequently being buried in a wave of soil). Surface soil velocities were uncorrelated with velocities on the tool surface, indicating that soil flow paths over the sweep were not para llel. The ratio of vertical to lateral soil flow at the tool surface i ncreased with larger rake angle and was greater than the ratio at the soil surface. At the soil surface, vertical velocity was greater near the nose than near the wing tip and velocity parallel to the travel di rection increased with increased speed and rake angle.