Essential Soil Physics An introduction to soil processes, functions, structure and mechanics

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

Preface
Introduction
Soils: integral part of our environment
Soil characteristics

1 Grain - size distribution: texture
1.1 Classification
1.1.1 Grain sizes
1.1.2 Grain shapes
1.1.3 Grain mixtures
1.2 Common soil textures and their origin
1.2.1 Equation of sedimentation
1.2.2 Separation processes
1.3 Spatial distribution of textures
1.4 Modification of grain size distributions in soils
1.5 Grain size distribution and other soil properties
1.6 Methods to measure grain size distributions
Problems Chapter 1

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

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

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

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

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

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

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

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

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

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

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

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

14 - References
Appendix

15 - Commonly used units and conversion factors
Meaning of abbreviations
Basic conversions: density and pore volume
Transport
Derivation of the heat-budget equation
Energy Budget at the soil surface
Tensors
Conversion of units
Keyword Index

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.