Effects of preferential flow induced by desiccation cracks on slope stability

Desiccation cracks on a soil slope can significantly increase permeability, reduce shear strength, and potentially result in shallow landslides. To reveal the slope failure mechanism induced by desiccation cracks, a full-scale model test was conducted on a cracked soil slope under rainfall–evaporation cycles. Image processing techniques were used to quantify the crack characteristics at the slope crest (SC), around the slope shoulder (SS), and at the slope foot (SF), and hydrologic sensors were used to monitor the moisture content, matric suction, and pore water pressure at different depths in the crack areas. The results showed dynamic variations in the desiccation crack patterns in accordance with their position on the slope and the rainfall–evaporation cycle. Preferential flow induced by the desiccation cracks in response to rainfall was detected earlier by the lower hydrologic sensors than the upper ones, and the desiccation cracks significantly increased the infiltration depth by up to four or five times the crack depth. Experimental evidence confirmed that preferential flow through desiccation cracks can trigger slope failure or landslides by forming local perched water zones near the crack tips. Based on this investigation, the failure process of the cracked soil slope was separated into three stages according to the crack patterns and failure modes: (I) generation of desiccation cracks, with surface erosion as the failure mode; (II) development and transformation of cracks, with flow-slip and local failure as the failure modes; and (III) renewal and further development of cracks, with overall failure as the failure mode. These conclusions suggest that when simulating the seepage and stability of a cracked soil slope, further modifications should consider the dynamic changes that occur within desiccation cracks. In addition, the use of specific treatment measures to avoid slope failure during the different stages is suggested.