中文摘要：

该文对不同耕地类型土壤表面干缩裂缝的发展规律进行了室内试验研究,通过计算机图像处理,研究裂缝形态的统计规律。结果表明：裂缝面积密度和长度密度都是随着含水率的减少而增大,达到最大值后保持稳定。水田和旱田试样的连通性指数随着含水率的减小而增大,分别在质量含水率为20%和12%左右达到最大值并且稳定,最大值分别为0.935和0.598,反映了不同耕地类型下土壤干缩裂缝网络的形成过程和连通性的实际情况。裂缝面积和长度的概率密度和累积概率符合正态分布,裂缝面积和长度的概率密度实测值与概率密度函数的拟合决定系数分别大于0.94和0.91;裂缝面积和长度的累积概率实测值与分布函数的拟合决定系数分别大于0.90和0.94。可以用正态分布描述土壤表面裂缝的形态,有助于研究土壤干缩裂缝的形成机理以及不同裂缝形态对土壤优先流的影响。

英文摘要：

Agricultural soil cracks generated during drying process becomes one of the causes of preferential flow. Generalizing crack network structure reasonably is an important research in the field. A laboratory experiment was carried out to investigate the law behind the development of shrinkage cracks on the soil surface under different types of cultivated land. In this investigation, computer image processing technique was applied to quantificationally analyze the statistical law of crack morphology and a dynamic description method based on normal distribution was proposed to depict the morphology of shrinkage cracks on soil surface. It showed that crack area density and length density both increased with decreasing moisture content and remained stable after reaching their maximums. Crack area density of paddy field （PF） specimen was a little bit bigger than that of upland field （UF） specimen throughout the drying process while the crack length density of both specimens didn＇t appear to be much different under the same mass moisture content. The connectivity index increased with decreasing moisture content and finally tended to be stable. The maximum connectivity index of PF specimen was 0.935 around a mass moisture content of 20% while for the UF specimen was 0.598 around a mass moisture content of 12%, reflecting that cracks of PF specimen were more closely connective to each other and the crack network of PF specimen formed faster. The connectivity index is applicable to account for the forming process and actual connectivity of shrinkage crack network under different types of cultivated land. Results suggested that crack area probability density and cumulative probability were in line with normal distribution. Both mean value and standard deviation had fairly good correlation with moisture content. Their coefficients of determination of UF specimen were larger than 0.99 and 0.98, respectively. The crack area coefficient of determination of different farmland types between the measured values and theoret