UBC Theses and Dissertations

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UBC Theses and Dissertations

Soil tillage studies with model plane chisels. Strong, Chester Ray


The physical characteristics of particle size distribution, compactability and plasticity of Ottawa sand and Haney clay were determined. Direct shear tests were used to relate dry bulk density, soil water content and normal pressure to the shear strength of Ottawa sand and Haney clay. The static and kinetic values of soil-metal friction were determined for each of three chisel shaped tillage machines with Ottawa sand and Haney clay. The friction values were then related to normal pressure, area of contact and soil water content for each soil. Tillage studies were conducted and the forces resulting from soil-machine interaction were measured. For each soil, these forces were related to soil water content, dry bulk density, machine width and machine velocity. The soil and chisel variables were combined in accordance with the Buckingham π theorem to form dimensionless ratios. These dimensionless ratios were combined to form equations for use in model-prototype predictions. The accuracy of these predictions was found to vary with soil water content, dry bulk density and machine velocity. Since all measurements recorded during the course of this study were analyzed by statistical procedures, the resulting equations do not represent basic physical relationships. Caution should therefore be used if these equations are to be applied to values beyond the range of values analyzed in this report.

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