Soil Cutting and Tillage

226 Pages·1985·5.063 MB·English

by  EDWARD McKYES (Eds.)

Developments in Agricultural Engineering 7
Soil Cutting and Tillage
OTHER TITLES IN THIS SERIES
1. Controlled Atmosphere Storage of Grains
by J. Shejbal (Editor)
1980 viii + 608 pp.
2. Land and Stream Salinity
by J.W. Holmes and T, Talsma (Editors)
1981 vi + 392 pp.
3. Vehicle Traction Mechanics
by R.N. Yong, E.A. Fattah and N. Skiadas
1984 xi + 307 pp.
4. Grain Handling and Storage
by G. Boumans
1984 xiii +436 pp.
5. Controlled Atmosphere and Fumigation in Grain Storages
by B.E. Ripp et al. (Editors)
1984 xiv + 798 pp.
6. Housing of Animals
by A. Maton, J. Daelemans and J. Lambrecht
1985 xii + 458 pp.
Developments in Agricultural Engineering 7
Soi l Cuttin g
an d Tillag e
EDWARD McKYES
Department of Agricultural Engineering, McDonald College of McGill University,
Ste-Anne de Bellevue, Quebec, Canada
ELSEVIE R
Amsterdam - Oxford - New York - Tokyo 1985
ELSEVIER SCIENCE PUBLISHERS B.V.
Sara Burgerhartstraat 25
P.O. Box 211,100 0 AE Amsterdam, The Netherlands
Distributors for the United States and Canada:
ELSEVIER SCIENCE PUBLISHING COMPANY INC.
52, Vanderbilt Avenue
New York, NY 10017, U.S.A.
ISBN 044442548- 9 (Vol. 7)
ISBN 0-44441940- 3 (Series)
© Elsevier Science Publishers B.V., 1985
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording or other
wise, without the prior written permission of the publisher, Elsevier Science Publishers B.V./Science
& Technology Division, P.O. Box 330, 1000 AH Amsterdam, The Netherlands.
Special regulations for readers in the USA — This publication has been registered with the Copyright
Clearance Center Inc. (CCC), Salem, Massachusetts. Information can be obtained from the CCC about
conditions under which photocopies of parts of this publication may be made in the USA. All other
copyright questions, including photocopying outside of the USA, should be referred to the publishers.
Printed in The Netherlands
í
CONTENT S
1. INTRODUCTIO N TO TILLAGE AND EARTHMOVIN G
1.1 HISTORY OF TILLAGE 1
1.2 MAIN TYPES OF TILLAGE TOOLS
1.2.1 Primary tillage 3
1.2.2 Secondary tillage tools 6
1.3 EARTHMOVING EQUIPMENT 8
1.4 THE ANALYSIS OF SOIL CUTTING AND TILLAGE 9
2. SOIL MECHANIC S
2.1 COULOMB'S LAW OF FRICTION AND COHESION 11
2.2 THE METHOD OF STRESS CHARACTERISTICS 16
2.3 BOUNDARY CONDITIONS 20
2.4 MEASUREMENT OF SOIL STRENGTH PROPERTIES 21
2.4.1 The direct shear box 22
2.4.2 The triaxial test 23
2.4.3 Field tests 27
2.5 SOIL BEHAVIOUR CONSIDERATIONS
2.5.1 Soil water pressure and movement 29
2.5.2 Critical state soil mechanics 32
2.5.3 Soil stress-strain behaviour 33
2.5.4 Shear rate effects 34
2.6 PROBLEMS 35
3· SOIL CUTTING FORCES
3.1 THE UNIVERSAL EARTHMOVING EQUATION 38
3.2 TWO DIMENSIONAL CASES: METHOD OF STRESS
CHARACTERISTICS
3.2.1 Smooth, vertical blade 38
3.2.2 Smooth raked blade in a cohesive soil · · 40
3.2.3 Rough raked blade in a cohesive soil 42
3.2.4 Boundary conditions between very rough and smooth · · · 44
3.2.5 Unconstrained tool to soil adhesion 46
3.2.6 The shape of failure surfaces 47
3.2.7 Including soil weight - Hettiaratchi's calculations . . .. 47
3.2.8 Approximation for soil with weight 49
3.2.9 Validity of the weightless soil assumption 51
3.3 THE METHOD OF TRIAL WEDGES 51
3.4 SIMILITUDE METHODS 54
3.5 THREE DIMENSIONAL CASES 55
3.5.1 Hettiaratchi and Reece (1967) 55
3.5.2 Godwin and Spoor (1977) 56
3.5.3 Three dimensional wedges (McKyes and Ali, 1977) . . .. 59
3.5.4 Grisso et al. (1980) 64
3.5.5 Comparison of the methods 66
VI
3.6 DYNAMIC EFFECTS 71
3.6.1 Inertial forces 72
3.6.2 Changes in soil strength 73
3.7 CRITICAL DEPTH 75
3.8 COMPLEX TOOL SHAPES
3.8.1 Curved tools 79
3.8.2 Shank and foot tools 80
3.8.3 The moldboard plow 81
3.8.4 Other tools 83
3.9 PROBLEMS 84
4. SOIL LOOSENIN G AND MANIPULATIO N
4.1 MEASUREMENTS OF SOIL LOOSENING 87
4.2 EFFICIENCY OF SOIL LOOSENING
4.2.1 Draft force efficiency 92
4.2.2 Loosening and pulverization efficiencies 95
4.3 SOIL MIXING AND INVERSION 98
4.3.1 Soil properties 99
4.3.2 Tool shape and speed 100
4.4 TOOL SPACING
4.4.1 Spacing and volume of soil disturbed 101
4.4.2 Tandem tool configurations 103
5. SOIL PROPERTIE S AND PLANT GROWTH
5.1 SOIL COMPACTION 105
5.2 MECHANICAL AND HYDRAULIC PROPERTIES OF
COMPACTED SOIL
5.2.1 Mechanical properties 112
5.2.2 Hydraulic properties 114
5.3 SOIL PHYSICAL PROPERTIES AND PLANT GROWTH 115
5.4 TILLAGE OF COMPACTED SOIL 123
5.5 PROBLEMS 124
6. TRACTIO N MACHINE S
6.1 FORCE AND ENERGY BALANCES
6.1.1 Forces on a traction machine 125
6.1.2 Energy balance at the machine-soil interface 127
6.2 TRACTION, SOIL DEFORMATION AND SLIP
6.2.1 Maximum traction force 129
6.2.2 Soil deformation and slip 131
6.2.3 Estimation of contact areas 134
6.3 SINKAGE AND ROLLING RESISTANCE
6.3.1 Sinkage in soil 135
6.3.2 Rolling resistance 140
6.3.3 Bekker's formulae 146
6.3.4 McKyes (1978) 147
6.4 MACHINE INTERNAL LOSSES 149
6.5 MATCHING MACHINES AND TOOLS 152
6.6 PROBLEMS 155
VII
REFERENCES 157
APPENDIX 1. Values of Í factors, two dimensions 162
APPENDIX 2. Values of Í factors, three dimensions 170
APPENDIX 3. Values of failure wedge angles 208
APPENDIX 4. Selected values of soil mechanical properties 212
AUTHOR INDEX 214
SUBJECT INDEX 216
This page intentionally left blank
Chapter 1
INTRODUCTION TO TILLAGE AND EARTHMOVING
1.1 HISTORY OE TILLAGE
Eor thousands of years of recorded history, groups of human beings have
been tilling the soil in order to increase the production of food. Early
evidence indicates that simple lightweight wooden plows, for instance, were
employed extensively in the valleys of the Euphrates and Nile Rivers by the
year 3000 B.C. Animals in the form of oxen provided the traction necessary
to" pull the plows, preparing the soil for the seeding of barley, wheat and flax
crops, (Encyclopedia Brittanica, 1979). The plows used during that period had
no wheels or moldboards with which to invert the soil and prepare a true plow
furrow. Nevertheless, they served to perform an initial breakup of the soil to
a shallow depth and subsequently to cover the seeds of the crop. An example
of an early Egyptian wooden plow is depicted in Eig. 1.1.
Eig. 1.1. Early wooden plow, Thebes, Egypt, circa 3000 B.C.
It was more than 2000 years ago that the first iron plows were fabricated
in Northern Honan, China. At first these were small hand-drawn tools having
a flat V-shaped iron piece attached to a wooden blade and handles. During
the first century B.C., water buffaloes were used to pull tillage implements.
Subsequently, triple-shared plows, plow-and-sow instruments and harrows were
developed.
Plows have been used also in India for thousands of years. Early
implements had no wheels or moldboard, being composed of wedge-shaped
hardwood blocks, and pulled by bullocks. The soil was broken into clods but
not turned over, and this primary tillage was followed by the passage of a
rectangular wooden beam, also drawn by bullocks, for the breaking of clods
and the levelling of the seedbed.
Iron plow shares appeared on Roman plows about 2000 years ago, as well
as cutting coulter knives. Still no moldboard was used to turn soil over. These
plows were pulled by teams of oxen, up to eight per team on a heavy soil
with high strength. There were reports, but no solid evidence, that plows
equipped with wheels appeared in Northern Italy around 100 A.D.