干湿循环对滑坡区黄土收缩性的影响规律

针对天山北麓山区黄土滑坡灾害,研究该区黄土湿陷干燥过程中的收缩特性和规律。通过对3种不同初始含水率土样的9次干湿循环下的收缩试验,获得收缩率和含水率随循环时间的关系曲线。通过对不同循环次数下土体收缩曲线的相似趋势进行拟合,获得该区不同循环条件下的黄土收缩曲线方程,得到一定含水率下线缩率与循环次数呈指数关系,随着干湿循环次数的增加最终线缩率变小;土体的线缩主要发生在直线收缩阶段,对这个阶段进行拟合得到表征干湿循环次数与收缩系数关系的线性回归方程,收缩系数随循环次数的增加而减小,且呈较好的指数关系;黄土的脱湿变形分为裂纹变形和收缩变形,利用PCAS软件分析干湿循环下土样表面裂隙规律,前三次循环试样边缘出现裂隙,到五次循环时,裂纹和收缩变形明显,第7次循环结束后,收缩变形进入稳定状态。

Study on the Effects of Drying and Wetting Cycles on the Shrinkage Characteristics of Loess in Landslide Area

The purpose of this study was to investigate the shrinkage characteristics and regularity of collapsible loess during drying process in the loess landslide disaster area in the northern foothills of Mt.Tianshan, China. Based on the shrinkage tests of three soils with different initial moisture content under 9 cycles of drying and wetting, the relationship curves of shrinkage rate and moisture content with cycling time are obtained. By fitting the similar trend of soil shrinkage curve under different cycles, the equations of loess shrinkage curve under different cycles in this area are obtained, the results show that the linear shrinkage of a certain moisture content is exponential with the number of cycles, and the final linear shrinkage decreases with the increase of the number of wet and dry cycles;The linear shrinkage of soil occurs mainly in the stage of linear shrinkage, and the linear regression equation which characterizes the relationship between the number of drying and wetting cycles and the shrinkage coefficient is obtained by fitting this stage, the results show that the contraction coefficient decreases with the increase of cycle times, and they show a good exponential relationship;The dehumidification deformation of loess can be divided into crack deformation and shrinkage deformation. The law of surface crack of soil sample under drying and wetting cycle is analyzed by PCAS software.SIt is concluded that the cracks appear at the edge of the specimen in the first three cycles, and the cracks and shrinkage deformations are obvious in the fifth cycle, and the shrinkage deformations enter a stable state after the seventh cycle.