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Highlighting some mechanisms of crack formation and propagation in clays on drying-path

It is common knowledge that clayey soils can crack during desiccation. Cracking occurs when soils are restrained while undergoing volume change produced as a result of the soil suction generated within the desiccating soil matrix. Desiccation cracking can have a severe impact on the performance of clayey soils in various geotechnical, agricultural and environmental applications. However, the essential mechanisms of desiccation cracking are not well understood, and consequently, predictive tools are inadequately developed. The mechanisms of drying shrinkage and associated cracking in soils, and the ways to control or avoid such cracking, are still elusive.
Kaolin which is a little swelling “nearly pure” kaolinite was studied in this research. The method is based on the determination of the local two-dimensional strains and displacements fields using the softwares VIC-2D. The objective of this research was to analyze the formation and propagation of cracks related to desiccation in clay and to provide a better understanding of the behavior. At the macroscopic level, the strain tensors of the two clays during drying, and the cracking phenomenon were studied using digital image correlation.
Different mechanisms of crack formation were identified: opening mode, sliding mode and tearing mode. At the end of desiccation, the cracks form a network similar to thermal fatigue or thermal shock networks. Bifurcation and coalescence of cracks can also be observed.

Author(s):

Xin Wei    
LMSSMat, UMR-CNRS8579, Ecole Centrale Paris
France

Lamine Ighil Ameur    
LEM3 UMR-CNRS7239, Université de Lorraine
France

Jean-Marie Fleureau    
LMSSMat, UMR-CNRS8579, Ecole Centrale Paris
France

Philippe Bompard    
LMSSMat, UMR-CNRS8579, Ecole Centrale Paris
France

Mahdia Hattab    
LEM3 UMR-CNRS7239, Université de Lorraine
France