Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Engineering Science (Interdepartmental Program)

First Advisor

Malcolm E. Wright


The performance of a vibrating digger blade machine was simulated in the laboratory and evaluated in the laboratory and in the field. The machine generated three modes of vibration: horizontal, vertical and their combination. A set of fifty-two tests replicated three times were performed in the field by varying amplitude (2 values), forward speed (2 values), and velocity ratio (2 values) for horizontal and vertical oscillation and amplitude combination (4 values), forward speed (2 values) and phase angle (4 values) for combined vibration. The tests were conducted in a silty-loam soil with the following characteristics: bulk density 1115.2 kg/m$\sp3$, moisture content from 22.4% to 26% db during the period of testing, cone index 0.509 MPa, cohesion and soil-soil friction coefficients of 24.77 kPa and 0.422 respectively, adhesion and soil-metal friction coefficients of 2.39 kPa and 0.464 respectively and plastic limit of 28%. The performance of the machine was evaluated by changes in the bulk density, geometric mean diameter of the resulting clods and their log standard deviation, torque, draft, and power ratio. For horizontal oscillation, forward speed was the factor with the most significant effect. Torque and power ratio increased, and bulk density and log standard deviation decreased as the forward speed increased. The velocity ratio did not produce the expected effects in reducing draft and increasing soil break up. In vertical vibration, there was moderate agreement between the simulation and the field results. Non-significant effects were obtained for most of the factors of evaluation for the levels of velocity ratio used, but there was an unexpected decrease in draft. In combined oscillation, the amplitude combination and the phase angle showed the greatest effects on the different factors. Phase angles of 180$\sp\underline{\circ}$ and 270$\sp\underline{\circ}$, respectively, and amplitude combinations with smaller amplitudes in the horizontal direction than in the vertical direction yielded the best performance. Compared to no vibration, the power increase ranged from 75% for vertical oscillation to 120% for horizontal vibration. The increase in power required to vibrate the soil was much higher than the decrease in power due to the decrease in draft.