Coupling effects of interfacial friction and layer thickness on soil desiccation cracking behavior

A series of desiccation tests were performed to investigate the effects of both interfacial friction and layer thickness on desiccation cracking behavior of soil. Nine groups of slurry specimens with different interfacial roughness and layer thicknesses were prepared and dried under a constant temperature of 30 degrees C. During drying, the change in water content was recorded and the dynamic process of soil cracking was monitored with a digital camera at different time intervals. Using digital image processing technique, the propagation characteristics of desiccation cracks on soil sample surfaces were quantitatively described with a series of geometric parameters. The results show that the initiation and propagation of cracks occur at relatively high water content ranging from 10% to 40% during drying. For the same soil layer thickness, the larger the interfacial roughness, the faster the propagation velocity of soil cracks. However, the influence of interfacial friction on soil cracking decreases with increase in soil layer thickness. Besides, there is a negative linear relationship between soil layer thickness and peak propagation velocity of soil cracks. During drying, the critical water content (wf, refers to the water content when the propagation of soil cracks tends to stabilize) decreases with increase in interfacial roughness under the same soil layer thickness. The final morphology of the desiccation crack network on each soil sample is significantly influenced by both the interfacial friction and soil layer thickness. The intensity of soil cracking increases with increase in interfacial roughness or decrease in soil layer thickness. These results also confirm that the effects of interfacial friction and layer thickness on soil desiccation cracking are coupled. Generally, the interface friction effect is more pronounced for thinner soil layers.