基于图像灰度化及二值化的数值处理技术，提出了膨胀岩裂隙度的概念及定量描述方法。在南水北调中线新乡潞王坟试验段进行了膨胀岩裂隙观测试验，定量分析了膨胀岩边坡在干湿循环中的裂隙的变化规律及其与含水率的相关关系。分析表明，膨胀岩裂隙的发育与天气变化密切相关，随着干湿循环的发展，裂隙的宽度和裂隙度逐渐增加，利用 Matlab 数字图像处理方法得到的裂隙率可以较好地描述裂隙的发育和发展情况

 On the basis of numerical processing technology of image grayscale and binarization , the concepts of crack rate and calculation method on expansive rock are presented. The dry-wet cycle tests were carried out in situ at Luwangfen test section of South-to-North Water Transfer Project Central Route, the tests focused on the observations of development changes in cracks and soil moisture changes. According to the results in the tests, the variation law of crack width on expansive rock slope and its relationship with moisture content during the dry  wet cycle test were quantitatively analyzed, also the variation law of crack ratio was investigated. The development of crack on expansion rock is closely related to changes in the weather, and with the development of wet and dry cycles, the width of cracks and crack ratio will gradually increase. By using the Mat lab digital image processing method, the crack ratio can be used to effectively describe the growth and development of cracks on expansive rock.