3D characterization of desiccation cracking in clayey soils using a structured light scanner

To capture the 3D morphological features of drying soils, we explore the potential of using a structured light scanner. Bentonite clay is used for desiccation tests. Both 2D images and 3D scans are obtained at certain time intervals throughout the test. We develop a post-processing methodology to quantify the 2D and 3D features of soil cracking, including surface crack ratio, total volume, surface area, and fractal dimension. Experimental results validate that the structured light scanner enables 3D high-resolution and accurate scanning of the soil desiccation cracking patterns. The change of 3D soil volume is more influenced by the widening of desiccation cracks, with slower soil volume reduction corresponding to the moment when primary cracks propagate vertically downwards. The spatiotemporal evolution of 3D reconstructed model indicates that the soil surface shrinks first, more in the central region and less along the boundaries due to the boundary constraint, before crack initiates and propagates. Both surface area and fractal dimension increase monotonically before the evaporation stops, with both more susceptible to the change of crack depth rather than crack width. Through presenting a new approach for soil desiccation cracking analysis, this study is expected to provide new insights into the soil desiccation process.