Study Of Effects Of Rain Infiltration On Stability Of Unsaturated Loess Slope

Landslide is closely related to rainfall, and for unsaturated soil slope the rain infiltration is the most important one that results in landslide. The stability of loess slop has aroused more and more attation with the development of the loess plateau area. But the study on effect of loess slope stability under rainfall is no so perfect. The variation of water distribution in unsaturated slope and the slope stability due to rain infiltration is studied in this paper. And the law of water-field distribution is analyzed theoretically under the influence of different factors such as the height the slope, the gradient of the slope, dry-density, water content, And then use the BISHOP method to calculate the stability of loess slope influenced by different factors.To study the influence of rainfall on the moisture of unsaturated loess slope, Firstly obtains the unsaturated soil - water characteristic curve and the saturated permeability-matric suction curve and determines its parameter through the text, then, unsaturated seepage analysis was performed. The result shows that the height of the slope takes little impact on the distribution of moisture content. But with the increasing of the height of the slope, the size of the field in which the moisture content increases increases . The steeper the slope is, the faster the seepage depth increase because of the rainfall, which decreases the stability of the slope. While the seepage field decreases with the increasing of dry-density of soil, which makes better stability of the slope. With the increasing of the moisture content, the seepage field and the moisture of the seepage field both increase. And with the increasing of rainfall duration, the seepage depth and the wet-sofe field of the soil both incrcases uncreasingly, which takes much effect on the stability of the slope. In the arid or half arid areas, there is less moisture in soil, the size of seepage field and moisture increase slowly, it is advantaged for the slope to resist rainfall infiltration. In the moist areas, there is more moisture in soil, the size of seepage field and moisture increase fastly, it is not advantaged for the slope to resist rainfall infiltrationSecondly, based on the water distribution obtained forward, the BISHOP method is complied to calculate the safety factor of the slope at different moments under rainfall infiltration. The result shows that the height of the slope increases, the safety factor of the unsaturated loess soil decreases because of the rain infiltration. With the rain infiltration, the heigher of the slope, the smaller of the safety factor. The gradient of the slope increases, the safety factor of the unsaturated loess soil decreases because of the rain infiltration. With the rain infiltration, the steeper of the slope, the more the safety factor decreases. The dry-density of the slope soil increases, the safety factor of the unsaturated loess soil increases because of the rain infiltration. With the rain infiltration, the bigger of the dry-density, the more the safety factor decreases. The dry-density of the slope soil increases, the safety factor of the unsaturated loess soil increases because of the rain infiltration. With the rain infiltration, the bigger of the dry-density, the less the safety factor decreases. The water content of the slope soil increases, the safety factor of the unsaturated loess soil decreases because of the rain infiltration. With the rain infiltration, the more of the water content, the more the safety factor decreases.In the arid environment, the depth of water infiltration of unsaturated loess slope is limited, which shows the water blocking role of the unsaturated soil, Affected by this, when the rain lasts one month, the safety factor that reduces is not significant, therefore, even in the rainy season, instability of so many Loess slope may be in connection with the accident on the Loess slope. If the rain lasts enough time, the soil reaches its saturation point, then the safety factor reduces significantly.