Abstract: Soils usually experience multiple drying-wetting cycles in nature, which can have a significant impact on the engineering properties of soils. Laboratory tests were conducted to investigate the effect of drying-wetting cycles on the initiation and evolution of cracks in clay layers. A clay specimen was prepared and was subsequently subjected to five drying-wetting cycles. The evolution of surface cracks during the drying-wetting cycles was monitored. The effect of drying-wetting cycles on the geometric characteristics of crack patterns was analyzed by the digital image processing software, and four geometric parameters, including the surface crack ratio, the total crack length, the average crack width and the intersection angle, were selected for the quantitative analysis. The results show that: i) The desiccation and cracking behavior can be significantly affected by the applied drying-wetting cycles. The cracks develop sequentially during the first drying process and the crack pattern exhibits typical hierarchical characteristics, while this phenomenon disappears in the subsequent drying-wetting cycles. ii) The edge of the cracks can break down and heal into "shallow ridges" during the wetting path. After the drying-wetting cycle most cracks occur at the original position, but the direction of cracking is different during different drying processes. iii) The drying-wetting cycles may cause the edges of the cracks to become rough and induce more tiny cracks in the soil specimen. iv) Drying-wetting cycles can advance the occurrence of the cracks in the specimen, increase the total length of cracks, decrease the average width of the cracks, but induce limited changes in the crack ratio. v) With the increase of drying-wetting cycles, the pattern of the intersections of the crack network gradually change from the T-junction to the Y-junction, while the intersection angle between cracks gradually changes from 90° to 120°.

Key words: desiccation cracking, drying-wetting cycle, crack network pattern, quantitative analysis, crack healing, crack intersection angle