Thoughts on modes of loess slope failure triggered by water infiltration and the principals for stability analysis
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摘要:
水对斜坡作用包括地表水流动作用和地表水入渗作用，地表水流动作用,如水库、河流的岸坡破坏，由水动力侵蚀所引起。目前黄土中地表水入渗影响下的斜坡稳定性分析存在一些概念含糊的问题，如忽略了入渗过程的应力路径，只考虑其破坏时的应力状态，这会导致对其破机理和稳定性计算参数取值的误判，文章只针对该类问题进行辨析讨论。黄土中地表水的入渗一般有降雨和灌溉两种，伴随降雨入渗多引起斜坡浅层破坏；灌溉导致地下水位上升则引起深层滑移。地表水入渗对斜坡总应力改变不大，水致斜坡破坏主要是孔隙水压力上升，土体有效应力降低所致。非饱和黄土中的初始孔隙水压力为负值，降雨入渗后的浅层黄土仍处于非饱和状态，孔压最大升到0；灌溉会引起地下水位抬升，潜水位下为正的孔隙水压力。明确了孔压变化过程，就可以用有效强度评价边坡稳定性。同时，目前一些观点认为关于流动性黄土滑坡是静态引起，这颠倒了因果关系，是滑移引起了液化，而不是液化导致的滑移。
Abstract:The action on water slope includes surface water flow and surface water infiltration, and surface water flow, such as slope damage of reservoir and river banks, is caused by hydrodynamic erosion. At present, there are some vague concepts in slope stability analysis under the influence of surface water infiltration in loess. For example, ignoring the stress path in the infiltration process and only considering the stress state at the time of its failure will lead to misjudgment of its failure mechanism and the value of stability calculation parameters. This paper aims to analyses and clarify the issues. There are two sources of groundwater in loess, those are rainfall and irrigation. Rainfall infiltration produces shallow slope failure during raining time, while irrigation causes groundwater level rising to trigger deep seated slide. Surface water infiltration can make a remarkable rising of pore water pressure, but minor change of the total stress, and a consequent decreasing of effective stress in the slope, which is the cause of slope failure triggered by water. The initial pore water pressure in unsaturated loess is negative, and the shallow loess after rainfall infiltration is still in unsaturated state, and the pore water pressure rises to 0 at the maximum. Irrigation will cause the groundwater level to rise, and the pore water pressure under the water table will be positive. When the change process of pore water pressure is made clear, the slope stability can be evaluated by effective strength. At the same time, at present, some opinions think that the landslide of flowing loess is caused by static state, which reverses the causality, and it is the slip that causes liquefaction, not the slip caused by liquefaction.
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Key words:
- loess slope /
- shallow failure /
- deep seated slide /
- rainfall /
- irrigation
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