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Modeling Soil Failure Caused by Prismatic and Conical Tools

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  031028,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13711) @2003
Authors:   Sun-Ok Chung, Kenneth A. Sudduth
Keywords:   Precision Agriculture, Sensor, Soil Strength, Cone Penetrometer, Modeling, Soil Failure

Soil strength, or mechanical resistance of a soil to failure, has been widely used to estimate the degree of soil compaction. Conventional measurements with cone penetrometers are laborious; therefore, we are working to develop an on-the-go soil strength profile sensor to collect data dense enough to show the spatial variability of soil strength in an efficient manner. Because soil failure involves complex interaction of many variables, determining design parameters of a soil strength sensor and interpreting test results would be improved with a theoretical understanding of the soil failure process. Mathematical models to estimate the force required to penetrate (cut and displace) soil with a prismatic cutter traveling horizontally and a cone penetrometer traveling vertically were developed based on the passive earth pressure theory. Both models were expressed as additive forms of density, cohesion, and adhesion components of the soil, with each effect multiplied by a corresponding dimensionless number. Graphic charts of dimensionless numbers were developed to investigate the behavior of each strength component at various values of soil internal friction angle, soil-metal friction angle, and cutting angle of the tool. The model for the prismatic cutter was validated with experimental results, and then used in simulation to optimize design parameters of the sensor, such as dimensions, and locations and spacing of sensing elements.

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