Agricultural Soil Mechanics

1 Soil Conditions.- 1.1 Strength-Determining Factors.- 1.2 Variation of Strength-Determining Factors in the Course of Time.- 1.3 Influences of Soil Type on Strength-Determining Factors.- 1.4 Soil Prepared for Laboratory Experiments.- 2 Mechanical Behavior of Soil Elements.- 2.1 General Aspects of the Mechanical Behavior of Soil Elements.- 2.1.1 Small Volume Elements Instead of Large Soil Bodies.- 2.1.2 Stress Theory.- 2.1.2.1 Stress Tensor.- 2.1.2.2 Mohr's Graphical Representation.- 2.1.2.3 Uniform Stress Distribution in Finite Soil Bodies.- 2.1.3 Strain Theory.- 2.1.4 Stress-Strain Relations.- 2.2 Elemental Treatment of Compaction.- 2.2.1 Occurrence of Compaction.- 2.2.2 Fundamentals.- 2.2.2.1 Measures of Compaction.- 2.2.2.2 General Model for Rapid Soil Compaction.- 2.2.2.3 Effects of Loading Rate, Repeated Loading, and Vibrations.- 2.2.2.4 Soil Physical Aspects.- 2.2.2.5 Slow Compression.- 2.2.3 Applications.- 2.2.3.1 Estimation of Soil Compaction by Means of Estimated Stress Distributions.- 2.2.3.2 Curve Fitting Formulas for Compression Tests.- 2.2.3.3 Håkansson's Compaction Test.- 2.2.3.4 Simulating Tire Effect by a Uni-Axial Compression Test.- 2.2.3.5 Predicting Soil Density Following Irrigation.- 2.2.3.6 Complexity of Compactibility Concept.- 2.3 Elemental Treatment of Deformation (Distortion).- 2.3.1 Occurrence of Distortional Strain.- 2.3.2 Fundamentals.- 2.3.2.1 Introduction.- 2.3.2.2 Deformation at Constant Volume.- 2.3.2.3 Distortion Combined with Compaction.- 2.3.2.4 Expansion at Breaking.- 2.3.3 Applications.- 2.3.3.1 Stress-Deformation Models.- 2.3.3.2 Determination of the Liquid Limit with a Rotary Viscosimeter.- 2.3.3.3 Distortion Combined with Compaction, Estimated Using the Flow Rule.- 2.3.3.4 Estimation of Distortion Combined with Compaction for Sand.- 2.4 Elemental Treatment of Breaking.- 2.4.1 Occurrence of Breaking.- 2.4.2 Fundamentals.- 2.4.2.1 Measures of Resistance Against Breaking.- 2.4.2.2 Shear Failure.- 2.4.2.3 Tensile Failure.- 2.4.2.4 Loading Rate and Repeated Loading Effects..- 2.4.2.5 Soil Physical Aspects of Shear Strength.- 2.4.3 Applications.- 2.4.3.1 Methods to Determine the Measures of Strength Indirectly.- 2.4.3.2 A Few Applications of the Modulus of Rupture.- 2.4.3.3 Draft Calculations Using Hypothesized Mechanisms of Rigid Soil Bodies.- 2.4.3.4 The Influence of Moisture Content at Seedbed Preparation on Plowing Resistance After Harvest.- 2.5 Elemental Treatment of Soil-Material Friction and Adherence.- 2.5.1 Occurrence.- 2.5.2 Fundamentals.- 2.5.3 Applications.- 2.5.3.1 The ?n-?1 Ratio of a Soil Element at a Soil-Material Interface.- 2.5.3.2 Attempts to Reduce Soil-Material Friction and Soil Adherence.- 3 Load Bearing and Soil Loosening Processes.- 3.1 General Aspects of Processes.- 3.1.1 Soil Tillage Processes Instead of Element Behavior..- 3.1.2 Description of the Variation of Forces and Movements in a Soil Tillage Process.- 3.1.2.1 Velocity Fields.- 3.1.2.2 Strain Fields.- 3.1.2.3 Stress Fields.- 3.1.2.4 Process Variations in Time.- 3.1.3 Basic Process Conditions.- 3.1.4 Prediction of Forces and Movements in Processes.- 3.1.4.1 Prediction Methods Mainly Based on Observations of Relationships Between Independent and Dependent Variables.- 3.1.4.2 Prediction Methods Mainly Based on Knowledge of the Mechanism of the Process Under Consideration.- 3.1.5 Types of Processes.- 3.2 Rollers, Wheels, and Tires.- 3.2.1 Occurrence.- 3.2.2 Fundamentals.- 3.2.2.1 Kinematic Aspects of Rolling Elements.- 3.2.2.2 Dynamic Aspects of Rolling Elements.- 3.2.2.3 Systems of Rollers, Wheels, and/or Tires.- 3.2.3 Applications.- 3.2.3.1 Estimating the Pull a Tire is Able to Develop.- 3.2.3.2 Estimation of the Mean Contact Stress of a Deflected Tire on a Rigid Surface.- 3.2.3.3 Estimation of the Area of Contact Between a Tire and a Rigid Surface.- 3.2.3.4 Relative Tire Deflection at Maximum Load.- 3.2.3.5 Optimal Slip Percentage.- 3.3 Penetrating Bodies (Wedges, Cones, Plates, Wires, Spheres).- 3.3.1 Occurrence.- 3.3.2 Fundamentals.- 3.3.2.1 Kinematic Aspects.- 3.3.2.2 Dynamic Aspects.- 3.3.3 Applications.- 3.3.3.1 Fitting Formulas for Plate Tests.- 3.3.3.2 Bekker's Sinkage and Rolling-Resistance Theory for Rigid Wheels.- 3.3.3.3 Correlations Between Cone Tests and Wheel Performance.- 3.3.3.4 Quick Determination of a Soil Mechanical or Physical Property.- 3.3.3.5 Determination of the Maximum Normal Stress That Has Ever Acted on a Soil Surface.- 3.3.3.6 Other Applications of Penetrometers.- 3.4 Sliding and Shearing Bodies.- 3.4.1 Occurrence.- 3.4.2 Fundamentals.- 3.4.2.1 Kinematic Aspects.- 3.4.2.2 Dynamic Aspects.- 3.4.3 Applications.- 3.4.3.1 Fitting Formulas for Shear Force-Horizontal Displacement Relationships.- 3.4.3.2 Resistance Approximations for Sliding and Shearing Bodies.- 3.4.3.3 Pull-Slip Relationships for Spaced-Link Tracks.- 3.4.3.4 Estimation of Rut Depth and/or Trim Angle of a Sled.- 3.4.3.5 Estimating c and ø Using Shear Plates or Annuli.- 3.4.3.6 Wall Friction of Cone Penetrometer Rods.- 3.5 Tracks, Cage Rollers, and Cage Wheels.- 3.5.1 Occurrence.- 3.5.1.1 Tracks.- 3.5.1.2 Cage Rollers.- 3.5.1.3 Cage Wheels.- 3.5.2 Fundamentals.- 3.5.2.1 Kinematic Aspects.- 3.5.2.2 Dynamic Aspects.- 3.5.3 Applications.- 3.5.3.1 Estimation of the Maximum Stress in the Contact Area of a Track on Soil.- 3.6 Tines.- 3.6.1 Occurrence.- 3.6.2 Fundamentals.- 3.6.2.1 Kinematic Aspects.- 3.6.2.2 Dynamic Aspects.- 3.6.3 Applications.- 3.6.3.1 The Profile of a Furrow Made by a Tine.- 3.6.3.2 Draft of Plane Blades and Tines Operating in a Saturated Clay.- 3.7 Plow Bodies.- 3.7.1 Occurrence.- 3.7.2 Fundamentals.- 3.7.2.1 Kinematic Aspects of Two-Dimensional, Curved Blade with a Small Cutting Angle and a Small Working Depth/Blade Height Ratio.- 3.7.2.2 Kinematic Aspects of Other Plow Bodies.- 3.7.2.3 Dynamic Aspects.- 3.7.3 Applications.- 3.7.3.1 Plowing Draft as Affected by Soil Moisture Content.- 3.7.3.2 Plowing Draft as Affected by Speed.- 3.7.3.3 Draft Force as Affected by Slades, Supporting Wheels, and Inclined Directions of Pull.- 3.7.3.4 Predicting Type of Intake from Unconfined Compression Tests.- Mathematical Treatment of Finite Homogeneous Strains in Two Dimensions.- References.