干湿效应下崩岗土体的裂隙演化及收缩变形规律

为提高崩岗土体稳定性，抑制崩壁崩塌。试验共设计6次干湿循环，利用工业相机对脱湿过程中崩岗4层土进行定时定点拍照并结合数字图像处理技术，研究干湿效应下崩岗土体的裂隙演化及收缩变形规律。结果表明：(1)脱湿过程中土体形态变化顺序为轴向收缩、径向收缩和裂隙发育；(2)表面裂隙率与液限、塑性指数、黏粒含量呈显著正相关关系，4层土中表面裂隙率最大值为过渡层18.78%,最小值为砂土层5.41%,崩岗土体剖面上两者为相邻土层，较大差异性会严重破坏崩岗的稳定性；(3)随干湿循环的进行，径向收缩不再发生，轴向收缩、表面裂隙率、裂隙平均宽度逐渐减小，裂隙总长度、裂隙总条数、裂隙交点个数、被分割的土块个数先增加后减小，各参数均在第3次干湿循环后趋于稳定，4层土中过渡层受干湿循环影响最大，砂土层最小。研究结果可为在降雨—蒸发反复交替过程中崩岗发生机理研究提供科学依据。

Crack Evolution and Shrinkage Deformation Rules of Benggang Soil Under Dry-Wet Cycles

In order to improve the stability of Benggang soil, prevent Benggang wall collapse, an experiment was conducted to study the crack evolution rules and shrinkage deformation rules of Benggang soil under the effect of Dry-Wet (D-W) cycles. A total of six D-W cycles were designed for the experiment, in which the four layers of soil were photographed at a fixed time and fixed site by using industrial cameras during the dehumidification process and in combination of digital image processing technology. Results showed as follows:(1) In the process of dehumidification, the sequence of soil morphology changes was:axial shrinkage, radial shrinkage, and crack development. (2) There was an obvious positive correlation between shrinkage cracking degree and liquid limit, plastic index and clay content. The maximum value of shrinkage cracking degree in the four layers of soil was 18.78% for the transition layer, and the minimum value was 5.41% for the sandy layer. The two soil layers were adjacent to each other on the section of the Benggang, and their great difference caused the terrible influence on the stability of Benggang. (3) As the D-W cycles, the radial shrinkage phenomenon no longer occurred. The rate of axial shrinkage, the rate of surface cracks, and the average width of the cracks gradually decreased. The total length of the cracks, the total number of crack strips, the number of crack intersections, and the number of lumps initially increased, then decreased, all parameters stabilized after the 3rd D-W cycles. Among the four soil layers, the transition layer was the most affected by D-W cycles, and the sandy layer was the smallest. These results could provide a scientific basis for the study on the mechanism of Benggang occurrence during the rain-evaporation cycles.