Effects of cracks on evaporation process of water in soils

Under the action of arid climate, the soils in the engineering are prone to develop shrinkage cracks, and the existence of cracks has an important influence on the engineering properties of the soils. In order to study the effects of cracks on the evaporation process of water in the soils, a series of laboratory evaporation experiments are carried out on the soils with cracks under simulated drought conditions. A series of samples with different crack numbers (0~3) and crack widths (5, 10 and 15 mm) are prepared by using the method of prefabricated cracks. Based on the results of water content and evaporation rate with drying time, the influence mechanism of crack numbers, widths and distribution characteristics on the evaporation process is analyzed. The results show that: (1) The cracks have a significant effect on the evaporation process of water in the soils; (2) The evaporation rate and the critical water content corresponding to the falling rate stage of the samples increase with the increase of the number of cracks. Under the crack width of 5 mm, the evaporation rate of the sample increases by about 14% for each additional crack, and the evaporation flux of the corresponding crack surface is about 15%~18% of the sample surface. (3) The evaporation rate of the samples and the evaporation contribution of the crack surface also increase with the increase of the crack width. The evaporation rate of the sample increases by about 2% for every increase of the crack width of 1 mm. When the crack width increases from 5 to 15 mm, the evaporation flux of the corresponding crack surface increases from 18% to 51% of the sample surface. However, the crack width has no effects on the critical water content when the samples enter the falling rate stage. (4) The effects of crack distribution on evaporation rate are mainly controlled by the relative humidity gradient and heat transfer in crack evaporation surface and crack cavity, and there may be a threshold effect of crack width.