Laboratory experiments on desiccation cracking of thin soil layers

This paper presents some experimental results on desiccation cracking tests conducted on thin layers of clay soils. Observation of the evolution of cracking patterns was examined to clarify the transient mechanisms of the crack formation of clay soils. Laboratory experimentation on desiccation cracking was carried out to examine experimentally the quantitative relationships between the characteristics of soil cracks and the prevailing controlling conditions. Five desiccation cracking tests for slurried clay soils were carried out using shrinkage moulds in a humidity chamber, which was capable of controlling relative humidity and temperature. The soil used in the experimental studies was residual basaltic clay and was classified as a highly reactive soil. In order to provide simple conditions for theoretical modelling, the tests were conducted in perspex and metal moulds with rectangular cross-sections. The lengths of the moulds were considerably larger than their widths so that parallel cracking were generated in thin layers. In each cracking test, several rectangular moulds of different thicknesses and widths were used. Some of these tests were used for observation, crack initiation and evolution, and others for moisture content measurement during desiccation. The test results include evolution of the cracking pattern, influences of speed of desiccation and typical crack spacing to depth ratios for soil layers.