| “5·12” Wenchuan earthquake induce thousands of shattered mountain,whichcreate the conditions for the formation of geological disasters after the earthquake.After the earthquake and the several rainy season a few years, geological disastersafter-effects appear gradually, hit the geological disasters are still endless, its impact isno less than the earthquake directly induced geological disasters. After the earthquake,Wenchuan geological disasters characteristics performance to required rainfall shorter,significantly less rainfall and intensity of geological disasters threshold wassignificantly reduced. Why after the earthquake, the geological disasters in thedisaster areas are so ordinary, and last longer. With these questions, taking niujinggoulandslide for example, rainfall-induced shattered mountain high-speed landslidecharacteristics were studied. Now this paper, the main results achieved and awarenesssummarized as follows:(1)Based on the development, sports and accumulation characteristics of theLandslide, Landslide is divided into the slip source region (I, including the slide areaI-1,residual area I-2), steep slope acceleration region (II, including the maincirculation area II-1,the right scraping slump district II-2, leftside scraping zone II-3),scraping long-distance flow region (III), the impact dispersal area (IV) andaccumulation areas (V). Landslide partitions and partition description carefully andobjectively show the entire movement of the landslide characteristics andperformance characteristics of high-speed remote.(2) According to the carefull investigation on the site, carefully count landslideshattered crack characteristics. Based on this classification of the cracks and makecracks Floor Plan. Crack deformation characteristics inferred through the deformationof the crack, plus post how slippery slope, rainfall led to the formation of the landslide. Cracks through a combination of not only controls the existing form of landslideborder but also plays the role of the further development of the post-landslide,showing the boundary effects of the earthquake cracks.(3) According to the site investigation of the degree of development of fracturesand penetration tests, ramp is divided into three regions.Sampled in each area,measured geotechnical parameters of the different samples. Test proved due to theimpact of the earthquake, landslide geotechnical the attenuation peak intensity greatlyreduced after the earthquake, almost before the earthquake residual strength values.Landslide permeability greatly increased, along with a high degree of development ofthe cracks, a prerequisite for subsequent rainfall conditions that triggered the landslideformed.(4) Using the finite element analysis software to simulate niujinggou landslidesinduced by8.24rainfall. Further analyze the body seepage field, stability, stress andstrain of the slope. Based on this assumption before the earthquake ramp model, tosimulate the effect of slopes by8.24rainfall before the earthquake. Comparativeanalysis can be seen through before the earthquake and after the earthquake. Due tothe increase in the permeability coefficient of the slope, rainfall into the slope seepagefield changes after the earthquake. The role of the pre-earthquake, landslide intensitygreatly attenuated, this landslide stability has been greatly reduced, coupled with thesoftening of the infiltration of groundwater, so that the slope of the shear weakenedagain, resulting in a8.24rainfall-induced landslides. However, assume that before theearthquake model, the slope is stable, not instability. At the same time, throughrepeated trial, calculated before the earthquake to cause slope landslides criticalrainfall. The results show that after the earthquake, landslide critical rainfall decreasedby about17%than before the earthquake.(5) By shock the crack boundary effects and earthquakes cause attenuation of therock mass strength.The analysis of the cause of the landslide mechanism is a commonresult of the earthquake and rainfall. Summed up the the class shattered mountain"Flayer type "shallow soil landslides Features. The type of landslide general side ofthe slope shattered by a powerful earthquake, deformation of rock and soil shatteredloose, lower intensity development along the ridge at the same time a large number ofshatter cracks. Due to the impact of the earthquake, a large number of controlling theappearance of cracks, with the latter creep under the action of gravity in itself, cracksfurther expansion, the formation of the embryo of a landslide. Attenuation of the rockmass strength, had a more stable slope becomes less stable or unstable. In addition, a large number of cracks and shattered loose rock and soil makes a lot of rain during therainy season into the slope change before the earthquake slope inside the seepage field,the rainfall on the mountain after the earthquake induced ability to further improve,leading to lower critical rainfall intensity.(6) Using the UDEC discrete element analysis software, reproduced niujinggoulandslide throughout the course of the campaign. According to the motioncharacteristics of the landslide over the whole process is divided into four stages①rainfall-induced landslides start-up phase,②the debris flow steep acceleration phase,③debris flow scraping long-distance migration stage,④energy dissipationreduction accumulation stage, each stage of the landslide-debris flow characteristics.On this basis, through a variety of theoretical formula to calculate the maximum speedof the landslide36.4to42.6m/s. Landslide along the speed and slip away from thecalculation, consistent results with field investigations. According to the calculationresults and field survey results show that the high landslide potential energy, favorableterrain, effects of debris flow and landslide material composition is a tremendouseffort groove to form a high-speed remote landslide. |
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