| The southwest region of China-the southeast region of Tibet,due to its unique geological environment and climatic conditions,provides conditions for the formation of debris flow disasters.In recent years,debris flow disasters have occurred frequently in this region,causing a significant impact on the local people.Especially,this region is in a critical period of infrastructure construction,and the development of debris flow disasters has become an important constraint restricting development.Based on the project of "Geological Hazard Risk Investigation and Evaluation in Chayu County",this paper studies the development,distribution characteristics,and disaster formation patterns of debris flow disasters in Chayu County,and simulates the disaster formation process of typical debris flow disasters,further explaining the disaster formation patterns of debris flow disasters in the study area.The main research results of this paper are as follows:(1)The natural and engineering geological conditions of the study area were analyzed:The relationship between debris flow and its development is analyzed in terms of topography,geological structure,engineering geological rock formations,and rainfall.Through analysis,it is known that the steep terrain,deep rivers,strong geological tectonic activity,severe weathering of rock masses,rich loose slope deposits,and strong rainfall in the rainy season from March to October are all conducive to the formation and development of debris flow disasters.(2)Distribution characteristics of debris flow disasters in the study area: 142 debris flow disasters are developed in the study area under the influence of regional geological environment conditions,most of which are rainstorm gully type debris flows in the development period.Using weighted information,the debris flow hazard susceptibility zoning of Chayu County in the study area was completed.The analysis showed that the debris flow prone areas along the Chayu River,Sangqu River,and Nujiang River are the three major debris flow prone areas in the study area.Based on the results of vulnerability zoning,it is found that most debris flow disasters are distributed in a zonal pattern along the river flow in the study area,widely distributed in areas with an altitude of 1500-3000 m,and also distributed in various towns and townships,with significant development and distribution in Shangchayu Town and Chavarong Township.(3)Debris flow formation mechanism and disaster formation mode: According to the different solid supply modes of debris flow disasters,the debris flow disasters in the study area are divided into gravity erosion supply mode,gully bed erosion supply mode,and slope erosion supply mode.Based on the study of the source formation mechanism,disaster formation mechanism,and typical damage modes of debris flow under various recharge modes,it is concluded that the three disaster formation modes are respectively: bank collapse,ditch blocking,collapse,or channel startup,impact,and river blocking modes;Unstable channel loose matter-channel startup,bottom erosion-siltation,river blocking mode;Slope erosion-channel startup or ditch blocking and collapse-siltation and river blocking mode.(4)Typical debris flow disaster formation process: Mass Flow software is used to simulate the disaster formation process of the typical debris flow disaster point(2 # debris flow in Zhimei Village,Zhuwagen Town)in the study area.It is concluded that under the condition of a 20-year rainstorm,the movement process is "creep(0-60s)-acceleration(60-1500)-deceleration(1500-1800s)-pause(> 1800s)",during which there are multiple sources involved,including bottom opening scouring The formation mechanism of various disasters,including ditch plugging and collapse,causes damage such as impact and siltation.Therefore,it can be further elaborated that the disaster formation mode of debris flow disasters in the study area can be composed of multiple material source formation mechanisms,disaster formation mechanisms,and destruction modes. |
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