Risk Assessment And Prevention Research Of Debris Flow In Guxi Gully, Wenchuan

After the Wenchuan earthquake, the area of earthquake outbreak debris flows inhigh frequency and large-scale, resulting in huge economic losses and casualties. Inorder to reduce the losses,part of the important debirs flows gullies that had beenoutbroken or potential risk have been controlled and have been achieved some results.However, due to lack of the awareness in post-earthquake debris flows hazard, evenno risk assessment, resulting in failure of the many control engineering bodies, whichbrings the potential risk to the quake zone residents.Therefore, the paper takes Guxi gully debris flow in Xuankou town,Wenchuancounty as the study object.After field investigation, author combined withhigh-resolution remote sensing image data of the debris flow gully remote sensinginterpretation, assisted by Arcgis software, launched a study of debris flow hazardassessment. Meanwhile, the basic features of the ancient creek debris flow density,flow velocity, flow and impact force of debris flow and kinetic parameters werecalculated by analysis of ancient Gully large quantity of stones, blocks, large diameter,works on the body and ditch mudslides Landang port construction is extremelydestructive capability. For this reason, the impact of the experiment through the flume,consider carrying large rocks to study the impact of landslides, mudslides large stoneimpact analysis feature, designed to optimize dam stopped and disaster similarstructure to provide references and ancient landslides Gully recommendations. Finally,the results of a comprehensive study of proposed engineering measures and programsGully ancient landslides governance recommendations to provide a reference for thenext creek ancient landslides governance and other debris flow disaster management.Paper research from the following aspects mainly:(1) A detail field investigation had been made in Guxi gully. Statistics of theamount and distribution of the trench provenance, provenance total storage capacityof approximately411.85×104m3, can mudslides dynamic reserves of about135.67×104m3. Investigated the main channel and tributary channel characteristics and debris flow early rains, mudslides early rains this total rainfall reached225.4mm, stimulaterainfall intensity is17.1mm/h. Combining Guxi gully debris flow disaster situations,it is considered storm debris flow gully. In the debris flow formation process, due tosteep terrain within the ditch, channel narrow, longitudinal drop large tributarylongitudinal slope were more than300‰, special terrain conditions for theconvergence of water and sediment to provide a favorable terrain conditions. After theearthquake, a lot of landslides, avalanches, unstable slopes and other adversegeological trench region’s development, providing a lot of loose material source ofdebris flow activity and heavy rain are factors that stimulate the formation of debrisflow.(2) According to the field survey of the channel disaster situations and HDsatellite remote sensing image data using arcgis get a long ditch, drainage area,elevation, etc. ditch domain parameters. Using single debris flow risk assessmentmethods and risk calculation formula, the Guxi gully debris flow risk were evaluatedto obtain the risk value is0.61, is highly dangerous. And the results of the evaluationand the risk characteristics of the channel field surveys were analyzed.(3) Select the location of the Guxi gully ditch provenance different particlecontent analysis conducted experiments and take the corresponding pieces of thecurve; Grading curve combined with the use of scholars calculated density values ofGuxi gully is1.95g/cm3; Typical cross-section along the channel selected for detailedinvestigation, using a laser range finder to get the channel cross-section width mudgot deep mud marks Act; The size and distribution of the channel in a large stone hadbeen investigated. Using rain-flood method to calculate the flow, velocity, impact andother parameters under heavy rain once in5years,10years,20years,100years in Guxigully debris flow. Get50years out of the debris flow volume of a solid is35.82×104m3, the maximum impact force of stone is578KN. The preparatory work for thedebris flow control provides the basis for the reference data.(4) The survey found that the channel dams have been full of debris flowdeposition and lost the use of blocking debris flows.But the impact of big stones ishuge, taking the security of the factory buildings and residents into account, we mustpay attention to governance projects chunks damaging effects of the big stones. Tothis end, the author uses the Gully debris flow impact shock test simulations to obtaincharacteristics of debris flow impact forces near the main line of the verticaldistribution, combined with the Wenchuan earthquake debris flow in the channel dams and dam failure modes of material survey data and Ansys software to assistaffected large stone dam mechanical shock and displacement corresponding numericalsimulation analysis. Consider the applicability of the principle of economy of ancientlandslides creek dams to optimize the structure improvements, the distance gullysection5h/6~h, suggested pouring the dam surface layer of reinforced concrete layerthickness of15~30cm; in overflow orofacial use of high-strength concrete plaster;distance gully h/12~h/2part, and suggested scrap steel plate covering recommendedancient creek debris flow control dams using a modified slurry dam to block insteadof expensive reinforced concrete dam.Finally, the engineering measures andgovernance proposals have been proposed in Guxi gully and draw up managementproject plan.