Water infiltration in a cracked soil considering effect of drying-wetting cycles

Infiltration is of great concern in many fields like hydrology, agriculture as well as geotechnical and geological engineering. This study aims to investigate water infiltration in a cracked soil. Infiltration tests were conducted on compacted soil samples with different cracking degrees by drying to various water contents. Three drying-wetting cycles were applied. Experimental results show that no desiccation cracks are observed in the first drying process while cracks initiate and propagate in the second and third drying processes. Different from the infiltration curve of the non-cracked soil sample consisting of two distinct stages, that of the cracked soil consists of three distinct stages, representing constant, rapid reduction and gradual reduction in infiltration rate, respectively. A modified equation is proposed to describe the infiltration behavior of a cracked soil considering the prehealing time of cracks. Furthermore, it is found that for the tested soil, 4% of surface crack ratio is a critical value. When surface crack ratio is smaller than the critical value, its influence on infiltration capacity is insignificant. Afterwards, the infiltration capacity increases dramatically with increasing surface crack ratio. Based on this observation, a piecewise function is proposed to characterize the relationship between the normalized infiltration capacity of cracked soil and surface crack ratio. Infiltration capacity also increases with decreasing initial water content and increasing number of drying-wetting cycles. In terms of steady final infiltration rate, it increases with increasing initial water content as well as increasing number of drying-wetting cycles, but is not affected by desiccation cracking.