Patterns of Desiccation Cracks in Saline Bentonite Layers

Abstract

Formation of cracks as a result of desiccation is a ubiquitous phenomenon in nature which is influenced by various factors including the environmental conditions, the properties of soil and the evaporating fluid. In this work, a comprehensive series of experiments is conducted to investigate the salinity effects on patterns formation during desiccation of bentonite layers. To do so, mixtures of bentonite and NaCl solutions were prepared with salt concentrations ranging from 3 to 15 %. The mixture was placed in a petri dish mounted on a digital balance to record the evaporation dynamics in an environmental chamber in which the ambient temperature and relative humidity were kept constant. An automatic digital camera was used to record cracking dynamics formed during the desiccation of clay layers. Results illustrated that the salt concentration had significant effects on the initiation, propagation, morphology and general dynamics of cracks. It was found that higher salt concentrations resulted in larger crack lengths due to the effects of NaCl on colloidal interactions among particles as well as the drying behavior. Additionally, using scanning electron microscopy, the influence of salt concentration on the patterns of cracks was investigated at different scales down to a few hundred nanometers. The present results provide new insights into the salinity effects on the cracking patterns and dynamics during desiccation of clay layers.

Laboratory characterization and discrete element modeling of shrinkage and cracking in clay layer

“…The initiation and propagation of cracks while drying are also determined by 50 some environmental factors. Salt concentration, relative humidity and temperature, which may 51 significantly change the water evaporation rate, could affect the formation of desiccation 52 cracking (Gebrenegus 2011;Hedan et al 2014;Shokri 2015). Cyclic freezing and thawing could 53 change the shape of the desiccation polygons (Lu 2016).…”

Quantitative Analysis of Spectral Response to Soda Saline-AlkaliSoil after Cracking Process: A Laboratory Procedure to Improve Soil Property Estimation

“…The bounded water film reduces the soil cohesion and the tensile strength [55], which also has a great influence on the internal friction angle and the shear strength of the soil [56][57][58]. In addition, the well-known diffuse double layer (DDL) thickness can also be considered as an important role in soil surface cracking, which always becomes thinner as the salt contents of soil samples increase and directly enhances the shrinkage and desiccation cracking of soils during water evaporation [59][60][61]. It can be seen from Figure 5 that surface states of soil samples cannot affect the morphology of the reflectance curves but can largely change the amplitudes of the curves.…”

Quantitative Research on the Relationship between Salinity and Crack Length of Soda Saline-Alkali Soil

“…In addition, the trend between salinity and crack length can also be described by considering a phenomenon referred to as the "diffuse double layer" (DDL), which has a significant effect on soil and is affected by soil salinity -especially ion content. When the salinity levels of soil specimens increase, the DDL thickness becomes thinner, which plays an important role in soil properties and directly controls the shrinkage and development of surface cracking during water evaporation [43][44][45].…”