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Karl Heinrich Hartge; Rainer Horn:

Essential Soil Physics

An introduction to soil processes, functions, structure and mechanics

Ed.: Robert Horton; Rainer Horn; Jörg Bachmann; Stephan Peth

2016. 391 pages, 186 figures, 24 tables, 17x24cm, 1040 g
Language: English

ISBN 978-3-510-65288-4, bound, price: 72.00 €

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Keywords

soilhydrologystabilityerosionsoil mechanicsgas budgetalbedo

Contents

Synopsis top ↑

Also available in softcover

Soils are the porous skin of the Earth with variable and complex structures composed of solid, liquid and gaseous phases. Being in close contact with the atmosphere, biosphere hydrosphere, and lithosphere, soils fulfill numerous functions as a filter, buffer, habitat for organisms and resource for raw materials and food rendering them as the basis for life on our Planet. Soils are subject to continuous transformations and their dynamic nature is important for the interaction of biological, biogeochemical and physical processes. At the same time soils are vulnerable and affected by human activity and often subject to degradation.

This textbook (based on the 4th, German language edition) introduces the reader gently but comprehensively to soil physical processes. The authors discuss both the origin and dynamics of soil physical properties and functions - volume-mass relations of the solid, water and gas phases, grain and pore size distributions, permeability and storage capacity for water, gases and heat - and finally soil deformation and strength in relation to mechanical and hydraulic stresses resulting in structural changes through compaction, kneading, slaking and soil crusting. Unlike other soil physics textbooks, soil mechanical properties are herein described in great detail, because otherwise it is impossible to understand and adequately quantify soil stability and the effects of soil deformation on soil physical functions.

The book treats the physics of water, gas and heat movement in soils and interactions with the solid phase at various scales and other factors in detail -- because these are considered the ultimate basis of any model of soil behavior.

Threats to soils worldwide ultimately endanger food security for a growing world population. Because of this, the effects of soil use and degradation on transport processes, soil stability and pore functions are discussed, and options for soil protection, conservation, and amelioration are addressed.

The authors close a gap between general soil science texts and very specialized treatments of foundation engineering by integrating the concepts of soil mechanics to achieve a comprehensive description of soil physical behavior. Traditional soil physics topics, such as soil – water – plant relations, soil hydrology and gas, heat and field water cycles are complemented by soil rheology, physicochemical and amelioration sciences. Well-known and recent advances in analytical approaches and methods are well explained to be of use to persons interested in improving plant growth and optimizing crop yield.

This book is valuable for researchers, upper-level undergraduate students, and graduate students of agronomy, soil science, horticulture, geo-sciences, environmental science, landscape architects and everybody interested in understanding the intricate physical processes which control and modify soil functions. Problems are provided at the end of each chapter to enable readers to develop soil physics related problem solving skills.

Table of Contents top ↑



Preface 9
Introduction 10
Soils: integral part of our environment 10
Soil characteristics 11



1 Grain size distribution: texture 13
1.1 Classification 13
1.1.1 Grain sizes 14
1.1.2 Grain shapes 16
1.1.3 Grain mixtures 17
1.2 Common soil textures and their origin 21
1.2.1 Equation of sedimentation 22
1.2.2 Separation processes 23
1.3 Spatial distribution of textures 25
1.4 Modification of grain size distributions in soils 26
1.5 Grain size distribution and other soil properties 27
1.6 Methods to measure grain size distributions 30
Problems Chapter 1 31



2 Soil structure and structural functions 33
2.1 Soil structure and internal morphology 33
2.2 Bulk density, particle density 35
2.3 Pore volume and void ratio 36
2.3.1 Theoretical quantities to describe pore volumes 37
2.3.1.1 Influence of grain size and shape on pore volume 37
2.3.1.2 Effect of particle size 38
2.3.2 Number of grain contacts 39
2.3.2.1 Relationship of contact number and pore volume fraction 40
2.3.2.2 Natural grain size distributions and aggregates 41
2.3.3 Influence of grain contact points on soil pedogenesis 41
2.4 Pore size distributions 44
2.4.1 Subdividing pore sizes 44
2.4.2 Shapes, sizes of pores, and modes of pore formation 47
2.4.3 Effects of pore size distribution on soil quality 48
Problems Chapter 2 48



3 Mechanical and hydraulic forces in soils 50
3.1 Stability and the spatial arrangement of grains 50
3.1.1 Forces and stresses in soils 50
3.1.2 Subdivision of the forces and stresses within soils 54
3.1.2.1 Particle weight 55
3.1.2.2 Loads transmitted by solid phases of soils 55
3.1.2.3 Weight (overburden) stresses transmitted within the solid phase 55
3.1.2.4 Forces between the surfaces of adjacent particles 56
3.1.3 Stresses in three-dimensional space 56
3.2 Soil strength: the balance of forces 57
3.2.1 Shear resistance, a soil property 57
3.2.1.1 Shear resistance of soils and their determination 57
3.3 Stress strain relationship and time-dependent settlement 63
3.3.1 Stress strain relationship in soils 63
3.3.2 Time dependent settlement behavior of soils 65
3.3.3 The meaning of neutral stresses during loading 66
3.4 Stress-, strain-, and deformation processes in three-dimensional space.68
3.4.1 Stress and strain in three-dimensional space 68
3.4.2 Stress propagation within soils 68
3.4.3 Base failure as the result of the active and passive Rankine state 71
3.5 Flow behavior of soils: stresses between individual soil particles 74
3.6 Influence of soil properties on shear resistance 79
3.7 Mechanical changes of soil structure 79
3.7.1 Effects of anthropogenic activities on soils 79
3.7.2 Effects of animal activity and plant growth 81
3.7.3 Freezing effects 83
3.7.4 Soil compaction in civil engineering and construction 83
Problems Chapter 3 84



4 Interactions between water and soil 86
4.1 Adsorption of water in soils 86
4.1.1 Adsorption mechanisms 86
4.1.2 Properties of water adsorbed on soil components 88
4.2 Flocculation and peptization of soil particles 89
4.3 Shrinkage of soils 91
4.3.1 Causes of soil shrinkage 91
4.3.2 Shrinkage in soils 94
4.4 Swelling of soils 95
4.4.1 Mechanisms of swelling: swelling pressure 96
4.4.2 Inhibition of swelling 99
4.5 Cracking up: crack formation in soils 100
4.6 Water as a factor of soil stability 103
4.6.1 Static water pressure 103
4.6.2 Flow pressure in soils 105
4.7 Wetting properties of soils 107
4.7.1 Causes and occurrence of inhibited wetting of soil particle surfaces 107
4.7.2 Contact angles and capillarity 108
4.7.3 Documenting wetting properties 111
4.7.4 Impact of wetting properties on the environmental and habitat functions of soils 113
4.8 Electrical flow potentials in soils 114
4.9 Aggregate shapes and functions 115
4.9.1 Natural aggregate-forming processes 116
4.9.2 Anthropogenic modification of soil aggregates 120
4.10 Effects of aggregate size, - shape and -age 120
Problems Chapter 4 122



5 Distribution and hydrostatics of soil water 123
5.1 Distribution and origin of water in soils 123
5.2 Forces in soil water 124
5.3 The groundwater surface as reference plane 126
5.4 Soil water potential 127
5.4.1 Total water potential and component water potentials 128
5.4.1.1 Matric potential Ψm 129
5.4.1.2 Gravitational potential Ψz 129
5.4.1.3 Osmotic potential Ψo 130
5.4.1.4 Overburden or load potential ΨΩ 130
5.4.1.5 Pressure potential ΨP 131
5.4.2 Combining component potentials 131
5.4.3 Instruments for measuring soil water potentials 132
5.5 Equilibrium water potential 134
5.6 Relationship between matric potential and water content 135
5.6.1 Effect of grain size distribution on the matric potential/water content relationship137
5.6.2 Influence of structure on the shape of the matric potential/water content relationship 137
5.6.3 Hysteresis of the matric potential/water content curve 139
5.6.4 Measuring matric potential / water content curves 139
5.6.5 Mathematical description of the matric potential–water content relationship 141
Problems Chapter 5 141



6 Movement of water within the soil 143
6.1 Water movement in water saturated soil 143
6.1.1 Fluid-dynamic phenomena in soils 143
6.1.2 Flow Fields 147
6.1.3 Boundary conditions and spatial limits of flow fields 147
6.1.4 One-dimensional flow 148
6.1.5 Two- and three-dimensional flows 150
6.2 Water movement in unsaturated soil 153
6.3 Transient flow 155
6.3.1 Hydraulic diffusivity 159
6.4 Hydraulic conductivity as a soil property 160
6.5 Vapor transport 168
6.6 Infiltration 169
6.7 Drainage 174
6.8 Evaporation 181
Problems Chapter 6 188



7 The gas-phase of soils 193
7.1 The energetic state of the gas phase of soils 193
7.2 Composition of the gas phase in soils 195
7.3 Transport processes in the gas phase of soils 196
7.3.1 Gas diffusion 197
7.3.2 Mass fluxes in the gas phase of soils 199
7.3.3 Redistribution of gas within the soil 199
Problems Chapter 7 201



8 Thermal behaviour of soils 204
8.1 Thermal properties of soils 204
8.1.1 Definitions 204
8.1.2 Heat capacity of soils 205
8.1.3 Thermal conductivity 208
8.1.4 Thermal diffusivity 210
8.1.5 Mechanisms of heat transport in soils 211
8.2 Modeling thermal conductivity 213
8.3 Techniques for measuring thermal properties 213
8.4 Phase transitions of H2O and their effects 214
8.4.1 Redistribution of water vapor by thermal flux 214
8.4.2 Freezing and the formation of ice 215
8.4.3 Freezing and water movement 216
8.4.4 Formation of structure 218
Problems Chapter 8 219



9 Combined water-, heat and gas budget of soils 221
9.1 The atmosphere–soil interface 221
9.1.1 Radiation components and radiation budgets 221
9.1.2 Energy budget at the soil surface 224
9.2 Dynamics and temporal variations of the soil water budget 226
9.2.1 Ground- and floodwater 228
9.2.2 Path of matric potentials 231
9.2.3 Parameters characterizing water budgets 236
9.2.3.1 Field capacity 236
9.2.3.2 Permanent wilting point 239
9.3 Heat budget 239
9.3.1 Temperature distributions in soils 240
9.3.2 Heat sources 241
9.3.3 Soil temperature variations 241
9.3.4 Cumulative effects on the heat budget 245
9.4 Gas budget of soils 247
9.4.1 How water content affects gas distribution within the soil profile 248
9.4.2 Seasonal variations of soil air 250
Problems Chapter 9 252



10 Plant habitats and their physical modification 255
10.1 Plant requirements in terms of water supply 255
10.2 Interaction of mechanical and hydraulic processes 258
10.2.1 Mechanical and hydraulic soil deformation 259
10.2.2 Pore function changes resulting from mechanical and hydraulic stresses 261
10.2.3 Interactions between hydraulic pore function and mechanical parameters 264
10.2.4 Effects of soil management on physical parameters 264
10.3 Modification of the hydraulic stress state 266
10.3.1 Drainage 267
10.3.2 Irrigation 270
10.3.3 Percolation 272
10.4 Modification of the mechanical stress state 273
10.4.1 Compaction 273
10.4.2 Loosening soils 274
10.4.3 Material rearrangement 275
Problems Chapter 10 277



11 Soil erosion 280
11.1 Soil erosion: general principles 280
11.1.1 Delamination of particles or aggregates 281
11.2 Approaches to preventing erosion 285
11.2.1 Erodibility of soils 286
11.2.2 Erosivity of wind and water 287
11.3 Erosion models 287
11.3.1 Soil erosion by water 288
11.3.2 Soil erosion by wind 290
Problems Chapter 11 290



12 Solute transport and filter processes in soils 293
12.1 Solute transport: basics 294
12.1.1 Breakthrough curves in porous media 294
12.1.2 Molecular diffusion 296
12.1.3 Convective flux and hydrodynamic dispersion 298
12.1.4 Adsorption 299
12.1.5 Convection-dispersion model of solute transport in soils 300
12.1.6 Additional factors influencing solute transport 302
12.1.7 Models describing solute transport 303
12.2 Filtering processes in soils 304
12.2.1 Filter types 304
12.2.2 Soils acting as filters 305
12.2.3 Filter efficiency 306
12.2.4 Optimizing filtering processes 308
Problems Chapter 12 309



13 Future Perspectives of Soil Physics 311
Solutions to the problems of chapters 1–12 319


14 References 347
Appendix
15 Commonly used units and conversion factors 373
Meaning of abbreviations 373
Basic conversions: density and pore volume 374
Transport 375
Derivation of the heat-budget equation 376
Energy Budget at the soil surface 377
Tensors 378
Conversion of units 379
Keyword Index 380

Short Description top ↑

This textbook introduces the reader gently but comprehensively to soil physical processes. The authors discuss both the origin and dynamics of soil physical properties and functions - volume-mass relations of the solid, water and gas phases, grain and pore size distributions, permeability and storage capacity for water, gases and heat - and finally soil deformation and strength in relation to mechanical and hydraulic stresses resulting in structural changes through compaction, kneading, slaking and soil crusting. Unlike other soil physics textbooks, soil mechanical properties are herein described in great detail, because otherwise it is impossible to understand and adequately quantify soil stability and the effects of soil deformation on soil physical functions. This book is valuable for researchers, upper-level undergraduate students, and graduate students of agronomy, soil science, horticulture, geo-sciences, environmental science, landscape architects and everybody interested in understanding the intricate physical processes which control and modify soil functions. Problems are provided at the end of each chapter to enable readers to develop soil physics related problem solving skills.