Syllabus with schedule of lecture and practical
FMPE 501
Soil Dynamics in Tillage and Traction
2+1
Objectives:
To have an understanding of the principles of soil mechanics as applied to interaction of tillage
tools and traction devices with soil in terms of soil forces and deformation during for soil cutting
and generation of traction.
Unit-I
Characterization of state of stress in a point: Derivation, representation by Mohr’s Circle.
Coulomb's law of friction and cohesion. Measurement of soil resistance properties: Direct shear
box, torsion shear apparatus, triaxial apparatus. Soil behaviour considerations: Soil water
pressure and movement. Critical state soil mechanics: Soil stress-strain behaviour, shear rate
effects.
Unit-II
Soil cutting forces: The universal earthmoving equation, two dimensional cases, smooth vertical
blade, smooth and rough raked blades in cohesive soil, unconstrained tool to soil adhesion. The
shape of failure surfaces. Hettiaratchi's calculations, effect of soil weight. Soil cutting force by
method of trial wedges.
Unit-III
Extension of theory to three dimension: Hettiaratchi, Reece-Godwin and Spoor. Three
dimensional wedges: McKyes and Ali, Grisso models. Dynamic effect: Inertial forces, change in
soil strength. Concept of critical depth. Complex tool shapes: Curved tools-shank and foot toolsmould board plough. Soil Loosening and manipulation: Measurement of soil loosening and its
efficiency. Draft force efficiency: Loosening and pulverization efficiency. Soil mixing and
inversion: Soil properties, tool shape, tool speed and tool spacing.
Unit-IV
Traction devices: Tyres, type, size, selection mechanics of traction devices. Maximum traction
force: Soil deformation and slip, estimation of contact areas. Sinkage in soil: Rolling resistance,
Bekker's formulae, McKyes formulae. Soil compaction by agricultural vehicles and machines.
Practical:
Measurements of soil shear strength by in-situ shear box apparatus and soil friction by friction
plate. Measuring cone penetrometer resistance and working out tractive coefficients for tyres.
Measurement of in-situ shear strength of soil by torsional vane shear apparatus. Solving
problems on stress in soil. Solving problems on soil properties. Solving problems of tool forces.
Problems on tillage tool forces, wheel slippage, tyre deflection, design and performance of
traction devices.
Course Outcome:
The student will be able to understand the principles that govern manipulation of soil by tillage
tools. The student will be able to apply the principles of soil mechanics to theoretically calculate
the forces on tillage tools during soil cutting and forces generated by tractor wheels.
References:
1. McKyes E 2016. Soil Cutting and Tillage: Vol 7. Developments in Agricultural Engineering
Elsevier R Science Publisher SBV.
2. Koolen, A J and Kuipers H 1983. Agricultural Soil Mechanics. Springer-Verlag ISBN
13:978-3-642-69012-9.
3. Gill W R and Van den Berg G E 1968. Soil Dynamics in Tillage and Traction.
4. Handbook 316, Agricultural Research Service, US Department of Agriculture, Washington
DC, 1968
5. John B L, Paul K T, David W S and Makoto H 2012. Tractors and their Power Units. 4th
Edition. Springer Science & Business Media, ISBN: 81-239-0501-7, ASAE ISBN: 0929355-72-5.
Theory schedule
UNIT-I
1. Characterization of state of stress in a point and its derivation in two dimension(Ag
engg soil mech P17-20)
2. Representation of stress by Mohr’s Circle and solving problems( Mc Keyes P13-16)
3. Coulomb's law of friction and cohesion and its representation by Mohr’s circle and
solving problems on Mohr’s circle(Ag Engg soil Mech P21-25)
4. Variation of planar stress in soil by method of stress characteristics( Mc Keyes P1619)
5. Boundary conditions for soil failure due to tillage tool(Mc Keyes P20-21)
6. Measurement of soil shear strength by direct shear box, and torsion shear
apparatus.(P21-23)
7. Measurement of shear strength by tri-axial apparatus, and techniques of field
measurement of soil strength (Mc Keyes P23-29)
8. Soil strength as influenced by pore water pressure.( MC keyes P29-32)
9. Introduction to concepts of critical state soil mechanics, soil stress strain behavior and
shear rate effects. ( Mc keyes P32-35)
UNIT-II
10. Plane failure of soil by tillage tool- plane Universal earth moving equation- meaning of
variables used.(Ag Engg soil Mech P192-194, Mc Keyes P38-40)
11. Soil cutting similarity between failure by inclined tillage tool and inclined retaining
wall, The general wedge theory if soil failure and Universal Earthmoving equation.
Sample problem. ( P143,144,192,193,194 – AG. Engg- Soil Mech,)
12. Two dimensional soil failure by tillage tools, analysis by method of stress
characteristics for smooth vertical blade (Mc Keyes P38,39,40)
13. Analysis of forces on smooth raked blade (Mc Keyes P 40,41,42)
14. Analysis of forces on rough raked blade in cohesive soil (Mc Keyes P42,43,44)
15. Boundary conditions for smooth to rough raked blade,( Mc Keyes P44,45,46)
16. Soil adhesion and its effect on soil failure, failure boundary, analysis with and without
considering soil weight(Mc Keyes P46,47,48)
17. 17.Soil failure by rough inclined blade, analysis with soil weight, (Mc Keyes
P49,50,51)
18. Soil cutting force by method of trial wedges (Mc Keyes P51,52,53)
UNIT-III
19. Three dimensional soil failure- concept of narrow and wide tool, Hettiaratchi and
Reece Model. (Mc Keyes P55,56)
20. Godwin and Spoor of three dimensional soil failure (Mc Keyes P56,57,58,59)
21. McKyes and Ali model of soil failure (Mc Keyes P59-63)
22. Soil failure model ,Grisso (Mc Keyes P64-66)
23. Effect of Inertial forces, soil failure and critical depth of tool-( Mc Keyes P71-76)
24. Forces due to curved tools, shank and foot tools and mould board plough.( Mc Keyes
P79-83)
25. Soil loosening by plane tillage tools.( Mc Keyes P87-92)
26. Draft efficiency in soil loosening and pulverization (p92-97)
27. Effect of soil properties, tool shape and speed and tool arrangement on soil Mixing and
inversion (P98-104)
UNIT-IV
28. Rollers wheels and tyres, their occurrence. ( Koolen P105-110)
29. Kinematic aspect of rolling element Wheel ground contact, velocity and path of point
on surface of wheel and area of contact ( Koolen P110-116)
30. Dynamic aspects of rolling element, Forces and torque (Koolen P119-123)
31. Estimation of pull developed by tyre, mean contract stress, area of contact,tyre
deflection and slip (Koole-133-139)
32. Bekker's sinkage and rolling resistance theory for rigid wheels,(Koolen 147-150)
33. Sliding action of sled, shearing action by track grousers, Shearing of soil by shear plate
and annuli, shear displacement relation,(Koolen P155-158,165-166)
34. Traction mechanics,
analytical and empirical approaches, ASAE Nomograph
(Kentucky lecture 13 P1-18)
35. Bekkers model of traction with illustration (Kentucky lecture P18 -37)
Practical schedule
1. Measurement of shear strength parameters of soils in situ using grouser plates
2. Measurement of Shear strength of soil by torsional shear apparatus.
3. Measurement of shear- displacement characteristics of soil by torsional shear apparatus
with angular displacement measurement.
4. Measurement of sinkage properties of soil by plate sinkage method
5. Measurement of cone penetration resistance with recording penetrometer
6. Measurement of contact patch of tractor on firm ground with tyre print method
7. Measurement of geometry of tractor implement system and mass distribution to
determine wheel support forces.
8. Measurement of slip of tractor under driving and braking condition
9. Solving problems ofn state of stress within soil in two dimension by Mohr’s Circle
10. Exercise in evaluating soil shear strength by triaxial apparatus.
11. Solving problems of soil reaction to flat blades using universal earthmoving equation.
12. Solving problems on soil reaction in two and three dimensional soil failure.
13. Writing programme to evaluate forces on narrow tillage tools using standard models
14. Measurement of draft of tractor mounted tillage tool in field by two tractor method or
tillage dynamometer method
15. Measurement of draft of simple tillage tool and relating to soil strength parameters.
16. Measurement of tractive performance of tractor / power tiller on road/ concrete using
two tractor method
17. Final practical examination