Breaking up the compacted layer to loosen the soil

Requiring high draft power and resulting inhigh soil disturbance

Discrete element modeling (DEM) to simulate the subsoiling process

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Source: www.fao.org

Discrete element method (DEM) To study the behavior of granular material Repeated application of Newton’s second law and a

force-displacement law More detailed study of micro-dynamics of material

Particle Flow Code in 3 Dimension (PFC3D) A commercial DEM software package Modeling problems in solid mechanics and granular flow

3Source: Itasca (2003)

To develop a PFC3D model to predict soil cutting forces and soil loosening

To calibrate model parameters of soil

To validate the model with field measurements

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6Source: Itasca (2003)

Depicted as a cylinder of cementatious material

Envisioned as a set of elastic springs

Transmitting both force and moments

Bond breaking

Young’s modulus of the bond unknown

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Soil particle› Range of particle size› Particle-particle friction

coefficient› Young’s modulus › Ratio of normal and shear

stiffness › Bulk density

Soil box› Length, width, and height

Parallel bond between soil particles

› Radius of the bond› Bond normal and shear strength› Young’s modulus (To be calibrated)› Bond stiffness ratio

Subsoiler› Soil-subsoiler friction coefficient› Subsoiler stiffness› Subsoiler travel speed› Tillage depth

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Field conditions: Oakville, Manitoba, Canada Tillage depth & speed: 300 mm, 3 km/h Clay soil

Data collection Soil cutting pressure Soil dry bulk density Soil total porosity

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10Sensing circle: 4.8 mm radiusSensing area: 71 mm2

FlexiForce sensors were used to measure the soil pressure on the subsoiler and to calibrate the model

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Side view of the field operationBack view of the model

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Successful simulation of soil behaviour with PFC3D in terms of soil-subsoiler interaction force measurements and soil porosity changes

Young’s modulus of 105 Pa for the soil bond giving the best match between the measured and predicted soil pressures

Appropriate method of simulating soil aggregates, not individual soil particles as “particles” in PFC3D when simulating agricultural clay soils

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Simulating soil cutting forces and soil loosening resulting from the ripper at different tillage depths

Validating the simulation results against the field measurements and the universal earthmoving equation

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