为跟踪极旱过程中黏土坝坡裂缝发展过程,以白龟山2014年遭遇极端干旱为例,通过模型试验,模拟强降雨及极干旱天气,测得试样土体在吸湿-脱湿过程中的基质吸力值并研究其变化情况,由此获得土样的土-水特征曲线用以分析坝坡稳定。研究结果显示:短期的干旱导致坝体表面失水,并不会影响到坝坡的稳定,而长期干旱生成的裂缝会在强降雨时成为雨水渗入坝体的快捷通道,使得坝坡土体的强度急速降低,严重影响大坝的稳定。当不断遭遇干旱降雨循环后,坝坡土体会变得松散,即使不遭遇极干旱天气也会很容易产生裂缝,给坝坡稳定埋下隐患。考虑到裂缝发展与含水率的变化密不可分,且裂缝又直接影响到坝坡土体的强度,因此可根据不同时段的土-水特征曲线判定大坝的稳定情况,据此可提出相应的保护措施。

To track the development of cracks in clay dam slope in extreme drought, we conducted model test to simulate the heavy rainfall and extreme drought condition at Baiguishan reservoir in 2014 as a case study. We obtained the changes in matric suction of slope soil during wetting and drying cycles, and analyzed the stability of dam slope according to the obtained soil-water characteristic curves (SWCCs). We conclude that the loss of water in dam surface caused by short-term drought does not affect the stability of dam slope; but cracks generated by long-term drought would become fast channels of rainfall infiltration in heavy rainfall, which drastically reduces the strength of slope soil and severely affects dam stability. Slope soil is loosened by continuous dry-wet cycles, and cracks are easily generated even not in extreme drought, both posing potential risk to the dam. Since crack development is closely related to the change of water content and has a direct impact on slope soil strength, we recommend to determine the slope stability and to propose corresponding protective measures according to SWCCs in different periods.