Essential Soil Physics (eBook)

Preface 10
Introduction 11
Soils: integral part of our environment 11
Soil characteristics 12
Grain size distribution: texture 14
Classification 14
Grain sizes 15
Grain shapes 16
Grain mixtures 18
Common soil textures and their origin 21
Equation of sedimentation 23
Separation processes 23
Spatial distribution of textures 25
Modification of grain size distributions in soils 26
Grain size distribution and other soil properties 27
Methods to measure grain size distributions 30
Problems Chapter 1 31
Soil structure and structural functions 33
Soil structure and internal morphology 33
Bulk density, particle density 35
Pore volume and void ratio 36
Theoretical quantities to describe pore volumes 37
Influence of grain size and shape on pore volume 37
Effect of particle size 38
Number of grain contacts 39
Relationship of contact number and pore volume fraction 39
Natural grain size distributions and aggregates 41
Influence of grain contact points on soil pedogenesis 41
Pore size distributions 43
Subdividing pore sizes 44
Shapes, sizes of pores, and modes of pore formation 46
Effects of pore size distribution on soil quality 47
Problems Chapter 2 48
Mechanical and hydraulic forces in soils 49
Stability and the spatial arrangement of grains 49
Forces and stresses in soils 49
Subdivision of the forces and stresses within soils 53
Particle weight 54
Loads transmitted by solid phases of soils 54
Weight (overburden) stresses transmitted within the solid phase 54
Forces between the surfaces of adjacent particles 56
Stresses in three-dimensional space 56
Soil strength: the balance of forces 57
Shear resistance, a soil property 57
Shear resistance of soils and their determination 57
Stress strain relationship and time-dependent settlement 63
Stress strain relationship in soils 63
Time dependent settlement behavior of soils 65
The meaning of neutral stresses during loading 66
Stress-, strain-, and deformation processes in three-dimensional space 68
Stress and strain in three-dimensional space 68
Stress propagation within soils 68
Base failure as the result of the active and passive Rankine state 72
Flow behavior of soils: stresses between individual soil particles 75
Influence of soil properties on shear resistance 80
Mechanical changes of soil structure 81
Effects of anthropogenic activities on soils 81
Effects of animal activity and plant growth 83
Freezing effects 84
Soil compaction in civil engineering and construction 85
Problems Chapter 3 87
Interactions between water and soil 88
Adsorption of water in soils 88
Adsorption mechanisms 88
Properties of water adsorbed on soil components 90
Flocculation and peptization of soil particles 91
Shrinkage of soils 93
Causes of soil shrinkage 93
Shrinkage in soils 96
Swelling of soils 97
Mechanisms of swelling: swelling pressure 98
Inhibition of swelling 101
Cracking up: crack formation in soils 102
Water as a factor of soil stability 105
Static water pressure 105
Flow pressure in soils 107
Wetting properties of soils 109
Causes and occurrence of inhibited wetting of soil particle surfaces 109
Contact angles and capillarity 110
Documenting wetting properties 113
Impact of wetting properties on the environmental and habitat functions of soils 115
Electrical flow potentials in soils 116
Aggregate shapes and functions 117
Natural aggregate-forming processes 118
Anthropogenic modification of soil aggregates 122
Effects of aggregate size, -shape and -age 122
Problems Chapter 4 124
Distribution and hydrostatics of soil water 125
Distribution and origin of water in soils 125
Forces in soil water 126
The groundwater surface as reference plane 128
Soil water potential 129
Total water potential and component water potentials 130
Matric potential m 131
Gravitational potential z 131
Osmotic potential o 132
Overburden or load potential 132
Pressure potential P 133
Combining component potentials 133
Instruments for measuring soil water potentials 134
Equilibrium water potential 136
Relationship between matric potential and water content 137
Effect of grain size distribution on the matric potential/water content relationship 139
Influence of structure on the shape of the matric potential/water content relationship. 139
Hysteresis of the matric potential/water content curve 141
Measuring matric potential / water content curves 141
Mathematical description of the matric potential–water content relationship 143
Problems Chapter 5 143
Movement of water within the soil 145
Water movement in water saturated soil 145
Fluid-dynamic phenomena in soils 145
Flow Fields 149
Boundary conditions and spatial limits of flow fields 149
One-dimensional flow 150
Two- and three-dimensional flows 152
Water movement in unsaturated soil 155
Transient flow 157
Hydraulic diffusivity 161
Hydraulic conductivity as a soil property 162
Vapor transport 170
Infiltration 171
Drainage 176
Evaporation 183
Problems Chapter 6 190
The gas-phase of soils 195
The energetic state of the gas phase of soils 195
Composition of the gas phase in soils 197
Transport processes in the gas phase of soils 198
Gas diffusion 199
Mass fluxes in the gas phase of soils 201
Redistribution of gas within the soil 201
Problems Chapter 7 204
Thermal behaviour of soils 206
Thermal properties of soils 206
Definitions 206
Heat capacity of soils 207
Thermal conductivity 210
Thermal diffusivity 212
Mechanisms of heat transport in soils 213
Modeling thermal conductivity 215
Techniques for measuring thermal properties 215
Phase transitions of H2O and their effects 216
Redistribution of water vapor by thermal flux 216
Freezing and the formation of ice 217
Freezing and water movement 218
Formation of structure 220
Problems Chapter 8 222
Combined water-, heat-, and gas budget of soils 223
The atmosphere–soil interface 223
Radiation components and radiation budgets 223
Energy budget at the soil surface 226
Dynamics and temporal variations of the soil water budget 228
Ground- and floodwater 230
Path of matric potentials 233
Parameters characterizing water budgets 238
Field capacity 238
Permanent wilting point 241
Heat budget 241
Temperature distributions in soils 242
Heat sources 243
Soil temperature variations 243
Cumulative effects on the heat budget 247
Gas budget of soils 249
How water content affects gas distribution within the soil profile 250
Seasonal variations of soil air 252
Problems Chapter 9 255
Plant habitats and their physical modification 257
Plant requirements in terms of water supply 257
Interaction of mechanical and hydraulic processes 260
Mechanical and hydraulic soil deformation 261
Pore function changes resulting from mechanical and hydraulic stresses 263
Interactions between hydraulic pore function and mechanical parameters 266
Effects of soil management on physical parameters 266
Modification of the hydraulic stress state 268
Drainage 269
Irrigation 272
Percolation 274
Modification of the mechanical stress state 275
Compaction 275
Loosening soils 276
Material rearrangement 277
Problems Chapter 10 279
Soil erosion 282
Soil erosion: general principles 282
Delamination of particles or aggregates 283
Approaches to preventing erosion 287
Erodibility of soils 288
Erosivity of wind and water 289
Erosion models 289
Soil erosion by water 290
Soil erosion by wind 292
Problems Chapter 11 292
Solute transport and filter processes in soils 295
Solute transport: basics 296
Breakthrough curves in porous media 296
Molecular diffusion 298
Convective flux and hydrodynamic dispersion 300
Adsorption 301
Convection-dispersion model of solute transport in soils 302
Additional factors influencing solute transport 304
Models describing solute transport 305
Filtering processes in soils 306
Filter types 306
Soils acting as filters 307
Filter efficiency 308
Optimizing filtering processes 310
Problems Chapter 12 311
Future perspectives of soil physics 313
Solutions to the problems for chapters 1–12 321
Solutions to problems in chapter 1 321
Solutions to problems in chapter 2 322
Solutions to problems in chapter 3 323
Solutions to problems in chapter 4 326
Solutions to problems in chapter 5 327
Solutions to problems in chapter 6 330
Solutions to problems in chapter 7 335
Solutions to problems in chapter 8 336
Solutions to problems in chapter 9 337
Solutions to problems in chapter 10 340
Solutions to problems in chapter 11 345
Solutions to problems in chapter 12 347
References 349
Commonly used units and conversion factors 376
Meaning of abbreviations 376
Basic conversions: density and pore volume 377
Transport 378
Derivation of the heat-budget equation 379
Energy Budget at the soil surface 380
Tensors 381
Conversion of data measured in different units 382
Index 383