The irrigation activity is often occurred in loess "yuan" region. This activity not only keeps changing the underground water infiltration area,but also obviously affects the stability of the slope at the edge of loess"yuan"("yuan"slope for short) ,and often causes landslide disaster. Taking a typical slope at the edge of loess "yuan" in Heifangtai,Yanguoxia,Yongjing county,Gansu province as an example, we put forward a concept called "Infiltration ratio of slope mass". For exploring the function of the evolvement feature of underground water phreatic stripe and analysing the relationship between groundw-ater phreatic stripe and the stability of slope,we investigated the characteristics of slope shape and un-derground water. We also carried out experimental analysis and numerical simulation. Two important con-clusions have been drawn:①there is an quadric relationship between the change of the frontal surface of the underground water infiltration area and the rise-fall of underground water level,i. e.,the rise of the frontal surface of the underground water infiltration area is related to the rising velocity of the under-ground water level,which presents positive correlation with time. The expression is s( x,t) =vtM( x,t) .②The "Infiltration ratio of slope mass"(ζ) is closely related to the stability of slope,and the'ζ' has an knee point:when ζ≤0. 170,the stability coefficient decreases slowly and has little influence on slope;when ζ≥0. 170,the stability coefficient decreases sharply and has obviously influence on slope.%黄土塬区灌溉是一种常见的人类活动,这种活动不仅会引起塬区地下水浸润带的变化,而且对黄土塬边斜坡(简称塬坡)稳定性影响显著,常常形成斜坡灾害(滑坡).以甘肃省永靖县盐锅峡黑方台黄土塬边典型斜坡为例,首次提出"坡体浸润比"的概念,并利用边界调查、实验分析、数值模拟等方法探寻地下水浸润带的演化特征,定量分析了地下水浸润带与塬坡稳定性的关系,得到2点重要结论:①地下水浸润带锋面位置变化与地下水位升降为函数关系.即,地下水浸润带锋面位置随时间的上升幅度与塬区地下水位上升速度有关,呈时间正相关,表达式为s(x,t)=vtM(x,t);②"坡体浸润比"(ζ)与塬坡稳定性密切相关,ζ存在拐点,当ζ≤0.170时,塬坡稳定系数缓慢降低,对塬坡稳性影响不明显;当ζ≤0.170时,塬坡稳定系数急剧降低,对塬坡稳定性影响显著.
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