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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #357623

Research Project: Enhancing Production and Ecosystem Services of Horticultural and Agricultural Systems in the Southeastern United States

Location: Soil Dynamics Research

Title: A shearing strain model for cylindrical stress states

item JOHNSON, CLARENCE - Auburn University
item BAILEY, ALVIN - Retired ARS Employee
item Way, Thomas - Tom

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2018
Publication Date: 2/14/2019
Citation: Johnson, C., Bailey, A., Way, T.R. 2019. A shearing strain model for cylindrical stress states. Transactions of the ASABE. 62(1):225-230.

Interpretive Summary: A shearing strain model for soil that includes soil behavior under compressive normal and shear stresses great enough to attain maximum compaction was developed. The model was developed for a clay and a clay loam, from triaxial data with various stress loading paths. This model relates the ratio of the maximum shear stress acting on the cylindrical sample to the major principal stress, to the ratio of the maximum natural shearing strain to the natural volumetric strain occurring after shear stress is initiated. The model accurately describes the shearing distortion of triaxial soil samples under cylindrical stress loading prior to yielding by plastic flow. This model predicts soil shearing strain for input stress states that realistically represent field conditions.

Technical Abstract: Soil compaction limits crop roots from reaching more soil to access water and nutrients, and reduces rates of water infiltration into soil, causing increased soil erosion. In continuum mechanics, strains are classified as either normal strains or shear strains. A normal strain occurs along a direction perpendicular to the face of an element and a shear strain is along a direction parallel to the face. Equations (models) which describe soil compaction can be developed using soil triaxial tests conducted in a lab. Using triaxial test data from a clay and a clay loam soil, equations which relate shear strain to the maximum natural shear stress, the major principal stress, and the natural volumetric strain were developed. This model of maximum natural shear strain when coupled with a model of natural volumetric strain developed previously, should be valuable for finite element analysis of soil response to applied loads. The shear strain model is expected to be useful in numerical methods, including finite element analysis, applied to interactions of mechanical components such as tires, tracks, and tillage components, with soil. The model should be helpful in improving the application of modeling to soil-machine interactions, and in promoting the accuracy and usefulness of simulation for equipment development.