中文摘要：

黄土滑坡机理是黄土地质灾害领域研究的热点,而黄土介质干湿演替水-力特性变化、地下水动力场响应以及由此造成的斜坡稳定性变化是其形成的关键。本文在黑方台非饱和黄土水-力特性测试的基础上,结合斜坡地带灌溉引起的非饱和渗流演化过程与发展趋势,探讨了这种滑坡的发育机制。结果表明：随着灌溉持续,长期的正水均衡场引起地下水位上升,包气带增湿后非饱和黄土的吸力下降,强度显著降低,同时饱和区孔压上升,斜坡地带水力梯度增大,提高了水流的渗透力,致使斜坡稳定性下降,斜坡稳定系数随地下水位上升呈线性降低,当地下水位升至55m时达到坡体极限平衡状态,遇有利触发条件即可能失稳滑动,但地下水位变化对最危险滑面位置影响较小。

英文摘要：

The mechanism of irrigation-induced loess landslide is one of the top topics of loess geo-hazard researches. Furthermore, the key areas are the hydraulic and mechanical property changes of loess after drying and watering alternation medium under irrigation condition, as well as the slope stability changes due to groundwater flow field response. This paper discusses the developing mechanism of irrigation-induced loess landslide in Heifangtai, which is on the basis of the hydraulic and mechanical property tests of unsaturated loess in Heifangtai, the unsaturated seepage evolving process and developing trend of the slope area due to irrigation. The results demonstrate the following. With the lasting of irrigation, long-term positive water equilibrium field can trigger the rising of the groundwater table. Moistening of the unsaturated zone leads the matric suction to decline and the strength to reduce drastically. Meanwhile, the thickness of the saturated zone increases. This causes build-up of porewater pressure as well as augmentation of the hydraulic gradient in the slope. The seepage velocity fastens. Hence the seepage force on the slope escalates too. Then the slope stability drops. The factor of slope stability declines linearly with the rising of groundwater table. The slope reaches limit equilibrium state when the groundwater table is close to 55m, under which condition it may slide under certain negative triggering factors. The groundwater table change, however, has limited impact on the critical sliding surface.