| Loess Plateau is the largest area covered by loess in the world, located in the north of central China. Loess plateau contains rich minerals and basin, and river valley land reclamation has a long history. It is the cradle of ancient Chinese culture and also one of the main hub ofmodern human activity.But under the influence of unique landform, the development of economyand agriculture are restricted inloess plateau areas.In order to rationally utilize the loess gully land, the government started to carry out the gully regulation project in Yanan since 2010.The gully slopes were built into multi-stair slopes and the redundant soli was backfilledin the gully as farmland.Considering the restriction of economic cost, this project only relied on the simple mechanical excavation to build slope, which caused a large number exposedof loess slope surface.At the same time, this project created a new type of soil erosion and geological disasters. After the rainstorm in Yanan 2013, the gully slope had a different degree of damage, including the slope erosion and the overall slumpunder the action of water.In this context we surveyedthe multi-stair slopes inYanan, and carried outartificial simulation rainfall experiment in indoor to quantitative analyzed the benefits of soil and water conservation measures quantitatively in the slope. At the same time we selected sites in the field to analyzestability of the slope.Through the study of this article, we got the following mainconclusions:(1)The research shown that rainfall intensity was the mail influencing factor of the slope soil erosion.The rainfall factorhad significant influence onYanangully multi-stair slopes’ development of slopes’ soil erosion.Laboratory test showed that under the condition of same rainfall, the heavy rain caused stronger erosion and had highererosion speed than the light rain in the model, at the same time, under the strong rain erosion development phenomenon had obvious differences with the light rain. There wasa rainfall intensity range to make the erosion phenomenon significantly different.(2)The drainage measure could protect the multi-stair slope significantly.It could guide the runoff effectively and reduce the surface erosion which was caused by the runoff from the top of the slope. At the same time, this measure could reduce the soil moisture content and make the soil strength weakening slowly, maintain the overall stability of the slope.(3) Revealed the influence of the adverse slope had two sides.The special platform shape of the slope where the edge of the platform was a little higher than the slope toe could effectively reduce the water and sediment to migrate downward from the slope surface, stand the water on the platform, slow the flow velocity and increase the infiltration time. At the same time soil moisture content was increased.(4) The research found that only influenced by water infiltration the slope could remain stable.Through the field observation of Yanan gully slope and the testing in Shi Jiahe, we found that the phenomenon that a lot of whole slope sliding was not common, usually in the form of partial sliding with the width of broken slope not more than 10 m. Found in the experiment the multi-stair slopeinduced only by water infiltration which caused the soil strength reductionwould not make the slope slide and the slope stability was still at a higher level, single stage of the slope was hard to appear the overall slope sliding phenomenon. |
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