Swelling and Evaporation Behavior of Expansive Soils Under Varying Drying Temperatures
摘要
Expansive soil is recognized for its swell-shrinkage when subjected to seasonal wetting and drying. The degree of drying temperature varies seasonally and regionally. Different temperatures may affect the rate of evaporation and the rate and magnitude of free swell. This paper presents the results from laboratory experiments conducted on two industrial soil types: bentonite and kaolinite, to investigate the swelling and evaporation behavior at different temperatures (20, 60, and 105 °C) after soil specimens were subjected to up to four wetting–drying cycles. For swelling tests on specimens prepared at optimum moisture content and maximum dry density, the results show that for high drying temperatures, specimens exposed to wetting–drying cycles exhibit some shrinkage at the beginning of the drying process, which becomes more pronounced for specimens exposed to a higher number of cycles. They also show that as free swell proceeds with time, a significant increase in free swell occurs, followed by a small slope of free swell increment. For bentonite, the free swell decreases with the wetting–drying cycles at low drying temperatures, while it increases in the first cycle, decreases in the second cycle, and remains unchanged after the third cycle at higher drying temperatures. However, for kaolinite, free swell decreases with the wetting–drying cycles regardless of the drying temperatures. By comparing the magnitude of free swell considering soil type, it is found that free swell for the bentonite soil is higher than that for kaolinite. On the other hand, for evaporation testing, samples prepared in an initially slurry state, higher drying temperature allows a higher evaporation rate and shorter duration; the rate significantly decreases at lower water content. Concluding that as the drying temperature increases, the magnitude of the evaporation rate increases and it peaks earlier, then it decreases and reaches its constant rate for a shorter duration. This indicates that even after a long drying duration, soil samples still preserved some water content. Considering soil type, the preserved water for kaolinite was much higher than that for bentonite under low drying temperature. Interestingly, at high drying temperatures, the preserved water exhibits only a slight difference between the two soil types. Furthermore, with the wetting–drying cycles, it is observed that the evaporation rate increases with the increase of these cycles and the differences are larger for higher drying temperatures.