It is commonly accepted that wetting–drying cycles have an effect on the soil strength behavior. Crack development in soil is observed by many engineers during wetting–drying cycles, which may give a good explanation for the change in soil strength. A series of laboratory tests were conducted in this study to investigate the desiccation crack development and the strength change law for silty clay subjected to different numbers of wetting–drying cycles. The results show that the desiccation cracks at the end of drying process developed in two stages: the stage of rapid growth and the stage of steady state. The change law of soil strength is similar to the cracking that decreases quickly in the former stage and slowly in the latter stage, which indicates that the cracking in the soil is the main reason for strength reduction. Based on the assumption of an isotropic and linear elastic soil mass at rest earth pressure conditions, an equation for the depth of desiccation cracking after different numbers of wetting–drying cycles was obtained with soil mechanics for unsaturated soils. Finally, the applicability of the equation was verified compared with the experiment results.
The biodegradable composite films were prepared from corn stalk microcrystalline cellulose as filler and chitosan as polymeric matrix. The crystallinity, the tensile properties and the thermal properties of the composites were tested. The results show that the tensile properties and thermal properties were improved with the addition of corn stalk microcrystalline cellulose. When corn stalk microcrystalline cellulose account for 10% of the chitosan quality, the initial decomposition and maximum weight loss rate temperature was raised by 13.19°C and 38.84°C, tensile strength increased by 83.55% and elongation at break increased by 77.38% compared to those of pure chitosan
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