摘要
为研究多级干湿循环条件下农田土壤干缩裂缝的演变特征，在室内试验基础上，结合数字图像处理技术对裂缝几何形态特征进行了统计与定量分析。结果表明，干湿循环后，土壤开裂位置不变，增湿过程中裂缝闭合规律也大致相似，但干燥初期裂缝开裂规律受第1级干湿循环影响明显。第1级干湿循环后，裂缝面积率在含水率为20％～30％时增速降低，约90％的裂缝长度发育集中在含水率大于30％时，连通性指数在含水率大于14％时近似匀速增大。随着干湿循环级数的增加，土壤开裂含水率逐渐减小，而干缩稳定时裂缝网络连通性有所增强，但裂缝网络形态大致相似，裂缝总长也保持稳定。此外，裂缝宽度与土壤开裂程度均呈递减趋势，且各裂缝的宽度逐渐趋向统一，将对裂缝优先流有所遏制，有利于土壤水分的均匀入渗。
Aiming to investigate the evolution characteristics of soil desiccation cracks with multiple dry - wet cycles, laboratory tests were carried out to quantitatively analyze the geometric and morphological characteristics of cracks. It indicated that the soil was cracked at the same position during each dry - wet cycle, and behaved a similar crack closure law. The crack ratio was decreased slowly before moisture content was increased to 12%, and decreased rapidly when moisture content reached 18%, while it was remained stable when moisture content was between 12% and 18%. Both the crack length density and connectivity index were decreased quickly after got a critical moisture content, which was reduced with the increase of dry - wet cycles, respectively, and kept constant before that. However, the initial cracking law was greatly affected by the first dry- wet cycle. Since the second cycle, the acceleration of crack ratio was decreased when the moisture content was changed from 30% to 20%, and about 90% of the crack was developed before moisture content reduced to 30%, and the connectivity index was increased at a constant speed when moisture content was larger than 14%. When the dry - wet cycles were increased, it can be concluded that： the crack morphology and length were kept stable; the cracking moisture content was reduced and the connectivity of crack network was enhanced, but there were no obvious differences; the average crack width and stable crack ratio were decreased gradually, and the average width tended to be the same, which weakened the crack preferential. The research result has practical guiding for cracked soil irrigation.
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2016年第12期172-177,252,共7页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金项目(51579069
51179050)
江苏省高校优势学科建设工程项目(YS11001)
高等学校学科创新引智计划(111计划)项目(B12032)
关键词
土壤
干缩裂缝
干湿循环
演变特征
几何形态特征
soil
desiccation crack
dry - wet cycle
evolution characteristics
geometric and morphological characteristics
