Erodibility of a crusted soil

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Table of contents

Chapitre 1 : Evaluation de l’érodibilité pour un sol encroûté et conséquences pour la modélisation de l’érosion
Erodibility of a crusted soil : asessment of controlling factors and consequences for erosion modelling. An example from the Loess Plateau of China
1. Abstract
2. Résumé
3. Introduction
4. Material and methods
4.1. Sampling sites
4.2. Sampling method
4.3. Measurements
4.3.1. Aggregate stability
4.3.2. Standard soil properties
4.4. Statistical analysis
5. Results
5.1. Variability of the aggregate stability
5.2. Comparison of aggregate stability for paired crust and under-crust samples
5.3. Variability of standard soil properties
5.4. Relationship between standard soil properties and aggregate stability
5.5. Relationship between standard soil properties and the difference in aggregate stability between crust and under-crust
6. Discussion
6.1. The aggregate stability of a crust is different from the aggregate stability of its undercrust material
6.2. Standard soil properties do not adequately predict aggregate stability
6.3. Consequences for erodibility assessment and erosion modeling
7. Conclusions
8. Acknowledgments
Chapitre 2 : Synthèse bibliographique des processus physico-chimiques affectant la stabilité structurale
Physico-chemical processes affecting soil aggregate stability : a review
Abstract
1. Introduction
1.1. Soil structure and aggregate stability
1.2. Factors and processes of aggregate stability variation
2. Physical and chemical processes involve in aggregate stability
2.1. Macro-aggregate scale
2.1.1. Slaking
2.1.2. Raindrop impact
2.1.3. Freezing- thawing
2.1.4. Differential swelling of clay
2.2. Micro-aggregate scale
2.2.1. Particle rearrangement during wetting drying cycles
2.2.2. Interlocking: frictional effect
2.2.3. Clay dispersion and flocculation
2.2.4. Dissolution and crystallisation
2.2.5. Age Hardening & thixotropy
2.3. Interactions between the processes during wetting and drying cycles
3. Summary of current knowledge and orientation of further investigations
3.1. Widely studied processes
3.2. Processes needing further researches
4. Conclusion
Synthèse et conclusion
Deuxième partie – Étude de terrain de la variabilité de la stabilité
structurale à pas de temps court. Évaluation de facteurs explicatifs.
Introduction
Chapitre 3 : Mesure de la variation de la stabilité structurale à pas de temps court. Conséquences pour l’estimation de l’érodibilité
Short term dynamics of aggregate stability in the field : consequences for erodibility assessment
Abstract
1. Introduction
2. Materials and Methods
2.1. Sampling sites
2.2. Monitoring setup
2.3. Sampling setup
2.4. Measurements
2.5. Statistical analysis
3. Results
3.1. Temporal variation of aggregate stability
3.1.1. Monthly variation of aggregate stability
3.1.2. Short time step variation of aggregate stability
3.2. Comparisons between aggregate stability values for the different treatments .
3.3. Relationships between aggregate stability variations for the different treatments
3.3.1. Relationship between MWD of the surface and MWD of the subsurface
3.3.2. Relationship between aggregate stability of two plots on the same site (upslope and downslope).
3.3.3. Relationship between aggregate stability of the Marcheville site and the La Gouëthière site
3.4. Relationship between aggregate stability and rain height
4. Discussion
4.1. Aggregate stability varied at short time step
4.2. Influences of the different treatments on aggregate stability temporal variability .
4.2.1. Difference between surface and subsurface samples aggregate stability
4.2.2. Difference between aggregate stability of two plots located on the same crop field
4.2.3. Differences between the aggregate stability of two field sites located in similar soil types
4.3. Relationship between aggregate stability variation and precipitation
4.4. Consequences for erodibility assessment and erosion modeling
5. Conclusion
Acknowledgements
Chapitre 4 : Evaluation des facteurs explicatifs de variation de la stabilité structurale à pas de temps court
Short term dynamics of aggregate stability in the field : assessment of explanatory factors to improve erodibility prediction
Abstract
1. Introduction
2. Material and method
2.1. Sampling sites
2.2. Monitoring and sampling setup
2.3. Measurements
2.3.1. Aggregate stability
2.3.2. Variables linked to biological activity
2.3.3. Variables associated with climate
2.4. Statistical analysis
3. Results
3.1. Aggregate stability
3.1.1. Marcheville site
3.1.2. La Gouëthière site
3.2. Explanatory variables
3.2.1. Variables linked to biological activity
3.2.2. Variables linked to climate
3.3. Relationships between aggregate stability and explanatory variables
3.3.1. Relationships between aggregate stability and biological variables
3.3.2. Relationships between aggregate stability and climatic variables
3.4. Prediction of aggregate stability variations
4. Discussion
4.1. Factors linked to biological activity
4.2. Factors linked to climate
4.3. Prediction of aggregate stability and consequences for erosion predictions
5. Conclusion
Compléments à la partie 2
Synthèse et conclusion
Troisième partie – Caractérisation du réarrangement particulaire comme processus physico-chimique de variation de la stabilité structurale lié aux cycles d’humidité
Introduction
Chapitre 5 : Effet des cycles d’humectation-dessiccation sur la contrainte interne, le réarrangement particulaire et la stabilité structurale
Wetting and dryning cycle effects on internal stress, particle rearrangement and soil aggregate stability
1. Introduction
2. Material and method
2.1. Soil aggregate cylinder preparation
2.2. Wetting-drying cycle parameters
2.3. Measurements
2.3.1. Sensors
2.3.2. Aggregate stability
3. Results
3.1. Water tension
3.2. Vertical strain
3.3. Internal stress
3.4. Aggregate stability
4. Discussion
4.1. Influence of wetting and drying cycles on aggregate stability
4.2. Quantification of the variables measured by the sensors
4.3. Non reversible behaviour and particle rearrangement
4.4. Processes induced by wetting and drying cycles
5. Conclusion