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 ....................................... 15
1.1.3 Grain mixtures ..................................... 17
1.2 Common soil textures and their origin ..................... 20
1.2.1 Equation of sedimentation .......................... 22
1.2.2 Separation processes ............................... 22
1.3 Spatial distribution of textures .......................... 24
1.4 Modification of grain size distributions in soils ......... 25
1.5 Grain size distribution and other soil properties ......... 26
1.6 Methods to measure grain size distributions ............... 29
Problems Chapter 1 ........................................ 30
2 Soil structure and structural functions ................... 32
2.1 Soil structure and internal morphology .................... 32
2.2 Bulk density, particle density ............................ 34
2.3 Pore volume and void ratio ................................ 35
2.3.1 Theoretical quantities to describe pore volumes .... 36
2.3.1.1 Influence of grain size and shape on pore
volume ......................................... 36
2.3.1.2 Effect of particle size ........................ 37
2.3.2 Number of grain contacts ........................... 38
2.3.2.1 Relationship of contact number and pore
volume fraction ................................ 38
2.3.2.2 Natural grain size distributions and
aggregates ..................................... 40
2.3.3 Influence of grain contact points on soil
pedogenesis ........................................ 40
2.4 Pore size distributions ................................... 42
2.4.1 Subdividing pore sizes ............................. 43
2.4.2 Shapes, sizes of pores, and modes of pore
formation .......................................... 45
2.4.3 Effects of pore size distribution on soil quality .. 46
Problems Chapter 2 ........................................ 47
3 Mechanical and hydraulic forces in soils .................. 48
3.1 Stability and the spatial arrangement of grains ........... 48
3.1.1 Forces and stresses in soils ....................... 48
3.1.2 Subdivision of the forces and stresses within
soils .............................................. 52
3.1.2.1 Particle weight ................................ 53
3.1.2.2 Loads transmitted by solid phases of soils ..... 53
3.1.2.3 Weight (overburden) stresses transmitted
within the solid phase ......................... 53
3.1.2.4 Forces between the surfaces of adjacent
particles ...................................... 54
3.1.3 Stresses in three-dimensional space ................ 54
3.2 Soil strength: the balance of forces ...................... 55
3.2.1 Shear resistance, a soil property .................. 55
3.2.1.1 Shear resistance of soils and their
determination ................................... 55
3.3 Stress strain relationship and time-dependent
settlement ................................................ 61
3.3.1 Stress strain relationship in soils ................ 61
3.3.2 Time dependent settlement behavior of soils ........ 63
3.3.3 The meaning of neutral stresses during loading ..... 64
3.4 Stress-, strain-, and deformation processes in three-
dimensional space ......................................... 66
3.4.1 Stress and strain in three-dimensional space ....... 66
3.4.2 Stress propagation within soils .................... 66
3.4.3 Base failure as the result of the active and
passive Rankine state .............................. 69
3.5 Flow behavior of soils: stresses between individual soil
particles ................................................. 72
3.6 Influence of soil properties on shear resistance .......... 77
3.7 Mechanical changes of soil structure ...................... 77
3.7.1 Effects of anthropogenic activities on soils ....... 77
3.7.2 Effects of animal activity and plant growth ........ 79
3.7.3 Freezing effects ................................... 81
3.7.4 Soil compaction in civil engineering and
construction ....................................... 81
Problems Chapter 3 ........................................ 83
4 Interactions between water and soil ....................... 84
4.1 Adsorption of water in soils .............................. 84
4.1.1 Adsorption mechanisms .............................. 84
4.1.2 Properties of water adsorbed on soil components .... 86
4.2 Flocculation and peptization of soil particles ............ 87
4.3 Shrinkage of soils ........................................ 89
4.3.1 Causes of soil shrinkage ........................... 89
4.3.2 Shrinkage in soils ................................. 92
4.4 Swelling of soils ......................................... 93
4.4.1 Mechanisms of swelling: swelling pressure .......... 94
4.4.2 Inhibition of swelling ............................. 97
4.5 Cracking up: crack formation in soils ..................... 98
4.6 Water as a factor of soil stability ...................... 101
4.6.1 Static water pressure ............................. 101
4.6.2 Flow pressure in soils ............................ 103
4.7 Wetting properties of soils .............................. 105
4.7.1 Causes and occurrence of inhibited wetting of
soil particle surfaces ............................ 105
4.7.2 Contact angles and capillarity .................... 106
4.7.3 Documenting wetting properties .................... 109
4.7.4 Impact of wetting properties on the
environmental and habitat functions of soils ...... 111
4.8 Electrical flow potentials in soils ...................... 112
4.9 Aggregate shapes and functions ........................... 113
4.9.1 Natural aggregate-forming processes ............... 114
4.9.2 Anthropogenic modification of soil aggregates ..... 118
4.10 Effects of aggregate size, -shape and -age ............... 118
Problems Chapter 4 ....................................... 120
5 Distribution and hydrostatics of soil water .............. 121
5.1 Distribution and origin of water in soils ................ 121
5.2 Forces in soil water ..................................... 122
5.3 The groundwater surface as reference plane ............... 124
5.4 Soil water potential ..................................... 125
5.4.1 Total water potential and component water
potentials ........................................ 126
5.4.1.1 Matric potential Ψm ........................... 127
5.4.1.2 Gravitational potential Ψz .................... 127
5.4.1.3 Osmotic potential Ψ0 .......................... 128
5.4.1.4 Overburden or load potential ΨΩ ............... 128
5.4.1.5 Pressure potential Ψp ......................... 129
5.4.2 Combining component potentials .................... 129
5.4.3 Instruments for measuring soil water potentials ... 130
5.5 Equilibrium water potential .............................. 132
5.6 Relationship between matric potential and water content .. 133
5.6.1 Effect of grain size distribution on the matric
potential/water content relationship .............. 135
5.6.2 Influence of structure on the shape of the
matric potential/water content relationship ....... 135
5.6.3 Hysteresis of the matric potential/water
content curve ..................................... 137
5.6.4 Measuring matric potential/water content
curves ............................................ 137
5.6.5 Mathematical description of the matric
potential-water content relationship .............. 139
Problems Chapter 5 ....................................... 139
6 Movement of water within the soil ........................ 141
6.1 Water movement in water saturated soil ................... 141
6.1.1 Fluid-dynamic phenomena in soils .................. 141
6.1.2 Flow Fields ....................................... 145
6.1.3 Boundary conditions and spatial limits of flow
fields ............................................ 145
6.1.4 One-dimensional flow .............................. 146
6.1.5 Two-and three-dimensional flows ................... 148
6.2 Water movement in unsaturated soil ....................... 151
6.3 Transient flow ........................................... 153
6.3.1 Hydraulic diffusivity ............................. 157
6.4 Hydraulic conductivity as a soil property ................ 158
6.5 Vapor transport .......................................... 166
6.6 Infiltration ............................................. 167
6.7 Drainage ................................................. 172
6.8 Evaporation .............................................. 179
Problems Chapter 6 ....................................... 186
7 The gas-phase of soils ................................... 191
7.1 The energetic state of the gas phase of soils ............ 191
7.2 Composition of the gas phase in soils .................... 193
7.3 Transport processes in the gas phase of soils ............ 194
7.3.1 Gas diffusion ..................................... 195
7.3.2 Mass fluxes in the gas phase of soils ............. 197
7.3.3 Redistribution of gas within the soil ............. 197
Problems Chapter 7 ....................................... 200
8 Thermal behaviour of soils ............................... 202
8.1 Thermal properties of soils .............................. 202
8.1.1 Definitions ....................................... 202
8.1.2 Heat capacity of soils ............................ 203
8.1.3 Thermal conductivity .............................. 206
8.1.4 Thermal diffusivity ............................... 208
8.1.5 Mechanisms of heat transport in soils ............. 209
8.2 Modeling thermal conductivity ............................ 211
8.3 Techniques for measuring thermal properties .............. 211
8.4 Phase transitions of H2O and their effects ............... 212
8.4.1 Redistribution of water vapor by thermal flux ..... 212
8.4.2 Freezing and the formation of ice ................. 213
8.4.3 Freezing and water movement ....................... 214
8.4.4 Formation of structure ............................ 216
Problems Chapter 8 ....................................... 218
9 Combined water-, heat-, and gas budget of soils .......... 219
9.1 The atmosphere-soil interface ............................ 219
9.1.1 Radiation components and radiation budgets ........ 219
9.1.2 Energy budget at the soil surface ................. 222
9.2 Dynamics and temporal variations of the soil water
budget ................................................... 224
9.2.1 Ground-and floodwater ............................. 226
9.2.2 Path of matric potentials ......................... 229
9.2.3 Parameters characterizing water budgets ........... 234
9.2.3.1 Field capacity ................................ 234
9.2.3.2 Permanent wilting point ....................... 237
9.3 Heat budget .............................................. 237
9.3.1 Temperature distributions in soils ................ 238
9.3.2 Heat sources ...................................... 239
9.3.3 Soil temperature variations ....................... 239
9.3.4 Cumulative effects on the heat budget ............. 243
9.4 Gas budget of soils ...................................... 245
9.4.1 How water content affects gas distribution
within the soil profile ........................... 246
9.4.2 Seasonal variations of soil air ................... 248
Problems Chapter 9 ....................................... 251
10 Plant habitats and their physical modification ........... 253
10.1 Plant requirements in terms of water supply .............. 253
10.2 Interaction of mechanical and hydraulic processes ........ 256
10.2.1 Mechanical and hydraulic soil deformation ......... 257
10.2.2 Pore function changes resulting from mechanical
and hydraulic stresses ............................ 259
10.2.3 Interactions between hydraulic pore function and
mechanical parameters ............................. 262
10.2.4 Effects of soil management on physical
parameters ........................................ 262
10.3 Modification of the hydraulic stress state ............... 264
10.3.1 Drainage .......................................... 265
10.3.2 Irrigation ........................................ 268
10.3.3 Percolation ....................................... 270
10.4 Modification of the mechanical stress state .............. 271
10.4.1 Compaction ........................................ 271
10.4.2 Loosening soils ................................... 272
10.4.3 Material rearrangement ............................ 273
Problems Chapter 10 ...................................... 275
11 Soil erosion ............................................. 278
11.1 Soil erosion: general principles ......................... 278
11.1.1 Delamination of particles or aggregates ........... 279
11.2 Approaches to preventing erosion ......................... 283
11.2.1 Erodibility of soils .............................. 284
11.2.2 Erosivity of wind and water ....................... 285
11.3 Erosion models ........................................... 285
11.3.1 Soil erosion by water ............................. 286
11.3.2 Soil erosion by wind .............................. 288
Problems Chapter 11 ...................................... 288
12 Solute transport and filter processes in soils ........... 291
12.1 Solute transport: basics ................................. 292
12.1.1 Breakthrough curves in porous media ............... 292
12.1.2 Molecular diffusion ............................... 294
12.1.3 Convective flux and hydrodynamic dispersion ....... 296
12.1.4 Adsorption ........................................ 297
12.1.5 Convection-dispersion model of solute transport
in soils .......................................... 298
12.1.6 Additional factors influencing solute transport ... 300
12.1.7 Models describing solute transport ................ 301
12.2 Filtering processes in soils ............................. 302
12.2.1 Filter types ...................................... 302
12.2.2 Soils acting as filters ........................... 303
12.2.3 Filter efficiency ................................. 304
12.2.4 Optimizing filtering processes .................... 306
Problems Chapter 12 ...................................... 307
13 Future perspectives of soil physics ...................... 309
Solutions to the problems for chapters 1-12 .............. 317
Solutions to problems in chapter 1 ....................... 317
Solutions to problems in chapter 2 ....................... 318
Solutions to problems in chapter 3 ....................... 319
Solutions to problems in chapter 4 ....................... 321
Solutions to problems in chapter 5 ....................... 323
Solutions to problems in chapter 6 ....................... 326
Solutions to problems in chapter 7 ....................... 331
Solutions to problems in chapter 8 ....................... 332
Solutions to problems in chapter 9 ....................... 333
Solutions to problems in chapter 10 ...................... 336
Solutions to problems in chapter 11 ...................... 341
Solutions to problems in chapter 12 ...................... 343
14 References ............................................... 345
15 Commonly used units and conversion factors ............... 372
16 Meaning of abbreviations ................................. 372
Basic conversions: density and pore volume ............... 373
Transport ................................................ 374
Derivation of the heat-budget equation ................... 375
Energy Budget at the soil surface ........................ 376
Tensors .................................................. 377
Conversion of data measured in different units ........... 378
Index ......................................................... 379
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