Study On The Influence Of The Prior Infiltration Channels On Loess Slope Stability

Geological disasters are natural environment change of objective existence; meanwhile they are unavoidable events during development of the human and society. The main types of geological disasters in loess plateaus are landslide, collapse and mud flow etc, the most common and hardest on human society is landslide. In the loess plateaus, most water levels of loess slopes lie under the bedrock, which form a very thick loess unsaturated-zone. Based on the former investigation, rainfall, especially heavy rains and storm rains, are main factor lead to loess landslide. According to these former studies, this paper concluded the rule of rainfall infiltration on unsaturated-zone loess slope, comprehensive outlined the limit equilibrium stability evaluation method considering matrix suction on unsaturated-zone loess slope.Based on the field investigation and indoor tests, we obtained the related soil parameters of slope. We renewed the topography of slope before landslide by collecting and analyzing the data. A 2-D model of finite elements in unsaturated zone has been built to simulate the scheme of three kinds of rainfall infiltration, found the water flow principle and water content changing principle on loess slope, at the same time we simulated the effect of prior infiltration channels on loess slope during the process of rainfall infiltration. Based on the simulation of rainfall infiltration rule, the model of slope stability analysis has been established; we calculated the slope stability state under different rainfall intensity and rainfall time by limit equilibrium method. This paper concluded the rainfall infiltration rule on loess plateau unsaturated-zone.The understandings are as follows:1 The prior infiltration channels are the important factor of disasters after rainfall on loess slope.2 Without the prior infiltration channels, the water flow by the slope surface after rainfall, has a small effect to the slope stablility.3 The feature of rainfall infiltration on slope:when it comes to surface runoff, rain converge into the prior infiltration channels and reach the deeper soil, and finally form a saturated-zone; it is easy to form perched water when it has aquitard or bedrock in saturated-zone.4 Stability analysis under different rainfall intensity and rainfall time on loess slope with the method of Morgenstren-Price considering matrix suction show that: with the prior infiltration channels, the saturated-zone or perched water in deeper soil formed by rainfall is the main factor of loess instability.