| After the Wenchuan earthquake,post-earthquake secondary disasters occurred frequently in earthquake areas.After the earthquake,several debris flow disasters occurred in Tutou Gully located in Miansi Town,Wenchuan County,seriously endangering the lives and properties of residents near the gully mouth.Therefore,it is necessary to investigate debris flow source and assess the risk of debris flow,so as to provide basis for debris flow disaster prevention and avoidance.By collecting relevant geological conditions,meteorological and hydrological data,as well as field geological survey,this paper determines the source of debris flow material.Based on GIS platform,fuzzy analytic hierarchy process is used for risk assessment,and fl O-2D software is used for debris flow dynamic analysis,and the following results are obtained:1.Based on the engineering geological conditions in the Study area of Chutougou,combined with the field investigation,the plane shape of debris flow gullies is irregular,the cross-section of gullies is v-shaped,and the overall slope of the valley is large,the main gullies are narrow,and the slope of gullies is more than 650‰.The circulation area is relatively open,and there are many loose material sources in the ditch,so there are some hidden dangers.There are 6 main branches in Chutougou,which provide a certain water source and material source for debris flow.2.Using the fuzzy analytic hierarchy process(AHP)to hoe gully has carried on the risk assessment,selection of the basin area,relative elevation difference,main gully length and watershed cutting density,maximum rushed out of the party,the main lithology in the basin,24-hour rainfall seven factors as the index,has carried on the risk assessment to hoe gully,the results show that the danger level of mudflow in Chutougou is high.3.Use FLO-2D software to simulate debris flow dynamics.Debris flow dynamic parameters simulated by FLO-2D software are determined by field investigation and analysis of debris flow related data.The numerical simulation software is used to invert the mud-rock flow disaster of "8.20" Chutougou Gully in 2019.According to the field investigation and evaluation,the mud-rock flow occurred once in 50 years.The simulation results show that the maximum velocity of mud-rock flow is 4.7m/s,and the velocity of outflowing gully is 4.4m/s.The total volume of rushed fluid is29.68×104m3.To debris flow accumulation scope verified,simulation accuracy was70.7%,the simulation result is accurate,and analyzed according to the results of the numerical simulation of Lan Dang debris flow velocity and flow depth distribution near dam,encountered in the process of debris flow movement Lan Dang dam formation deposition,the first after so Lan Dang dam swim deep distribution characteristics of debris flow is the closer Lan Dang dam deep mud.The maximum depth of mud reached about 14 meters.The characteristics of flow velocity distribution of debris flow downstream of retaining dam are that the flow velocity of debris flow near retaining dam increases,which is due to the potential energy accumulated from debris flow movement to retaining dam.After the retaining dam is piled up,debris flow fluid flows out of the dam roof.The height difference of retaining dam makes debris flow fluid potential energy convert to kinetic energy,and the flow velocity increases.Compared with the actual situation,the simulation results are basically consistent with the actual situation.4.Topographical DEM data after mudflow occurred in Chutougou valley on August 17,2020 were used to simulate the movement process of mudflow after the failure of retaining dam.The outflow silted up the whole Minjiang River,and the accumulation range was much larger than that of retaining dam,resulting in a more serious disaster. |
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