| Secondary disasters occur when landslides clog up mountain valleys or river channels and store water to a certain extent in landslide dam.Landslide dam will not only cause flood disaster upstream,but also has the risk of break,once the landslide dam is destroyed,the lake water forms the flood,to the downstream people's life and property serious threat,very dangerous.The process of dam break is not only the key point of disaster research,but also the key content of dam stability evaluation and prediction.In this paper,31 landslide weirs are selected as the research objects,and their development characteristics and dimensions are analyzed statistically.Based on the grain gradation of zongqu dam in Maoxian County,Sichuan Province,the basic grain gradation is obtained after scaling,and 13 groups of different dam materials are prepared.Then direct shear test and permeability test are carried out according to different dry density,gradation and fine particle content.Finally,the model test of the artificial barrier dam is carried out.By analyzing the video data of the side and front failure modes of the dam in the model test,the rules of the development process,failure process and break-out process of different dam materials are obtained.The main achievements of this paper are as follows:(1)Statistical analysis of development characteristics and size characteristics of landslide dam.Taking 31 landslide dams as statistical samples,it is shown that the material source landslide of the dam is mostly triassic(T),the lithology is mainly sandstone,and the scale of the landslide dams is mostly large or very large.Most of the dammed dams are located in Sichuan Province,which is prone to form landslide dammed by frequent and strong earthquakes,followed by rainfall.(2)Study on shear strength and permeability of different dam materials.The influence of dry density,gradation and fine particle content on shear strength index and permeability of sand is obvious.With the increase of dry density,the inner friction angle increases and the permeability coefficient decreases,while the inner friction angle of well-graded sand is larger than that of poorly-graded sand,and the permeability coefficient of well-graded sand is smaller than that of poorly-graded sand,the coefficient of permeability decreases with the decrease of internal friction angle.The shear strength and permeability of clay-bearing and sand-bearing soils are basically consistent.(3)Model test of artificial barrier dam.Dry density,good gradation and fine particle content have significant effects on the development of saturation line of sand and clay-bearing barrier dams.The development process of the saturation line of the dam with different materials is as follows:the development rate of the saturation line of the sand dam and the clay dam increases with the decrease of dry density and the decrease of the fine particle content;the development rate of saturation line of poorly graded sand barrier dam and clay-bearing barrier dam is higher than that of well graded sand barrier dam and clay-bearing barrier dam.(4)Study on failure process of artificial barrier dam model test.The dry density,good gradation and fine particle content have significant effects on the failure process of sand and clay dammed dams.The smaller the dry density is,the more easily the sand barrier dam and the clay-bearing barrier dam will fail,and the shorter the duration of the downstream dam failure is,the more easily the sand barrier dam will slide,and the dry density of the sand barrier dam is smaller,which shows the retrogressive failure from downstream to upstream,compared with well-graded sand barrier dam and clay-bearing barrier dam,sand barrier dam with high dry density and clay-bearing barrier dam have the same failure mode,but the sand barrier dam with high dry density has the same failure mode from the top to the downstream,the dammed dams with bad gradation of sand and clay are easy to be damaged,and the dammed dams with bad gradation of sand are easy to be damaged.The dammed dams with bad gradation of sand are easy to be damaged,and the dammed dams with bad gradation of sand are easy to be damaged,the smaller the content of fine particles,the easier it is to damage the sand dammed dam and the dammed dam with clay,and the shorter the damage duration of the downstream dam,the easier it is to slip,the failure mode of sand barrier dam with small fine particle content is backward multiple times from downstream to upstream,while the failure mode of sand barrier dam with large fine particle content is large circular arc multiple times.(5)Study on break process of artificial barrier dam model test.The dry density,good gradation and fine particle content have significant effects on the failure process of sand and clay dammed dams.Based on the analysis of 13 groups of material dam test videos,the dam break stage is divided into 4 stages:downstream dam surface erosion,gully erosion,mouth break collapse and normalization.As the dry density decreases,the erosion resistance of the dam surface decreases,and gullies are easy to form.The earlier the two side walls of the gullies form a hanging surface,the more unstable and unstable the break is,and the shorter the duration of the break is,the erosion resistance of the cofferdam surface of sand with poor gradation is weaker,and it is easy to form gullies,the breach is easy to collapse,and the duration of the break is short,it is easy to collapse repeatedly at the breach,and the duration of the breach is longer.The change law of the clay-bearing barrier dam is basically the same as that of the sand-bearing barrier dam.Figure[54]Table[20]Reference[65]... |
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