The Research On The Development Characteristics And Ecological Contrul Of Wuhuahai Debris Flow In Jiuzhai Scenic Area

In this paper,the debris flow in Wuhuahai after the Jiuzhaigou earthquake is taken as the research object.Based on the reliable background datas obtained through field investigation,the development characteristics,genetic mechanism and dynamic parameters of the debris flow in Wuhuahai are analyzed and calculated.At the same time,according to the research results of domestic and foreign literatures,it is determined to adopt the dynamic analysis software-DAN3D and Voellmy model to simulate the whole process of debris flow in wuhuahai,and to study the movement process of the debris flow.In addition,according to the development of the debris flow and the vegetation and soil conditions in the gully area,the project managements and ecological restoration schemes are determined.Following are the main conclusions of this paper:(1)Wuhuahai debris flow is located next to Wuhuahai,a famous scenic spot in Jiuzhaigou scenic area.The gully area looks like leaf shape,and the basin area is 2.6km~2.The the length of main gully is 0.85km,the average longitudinal gradient is 434‰,and the relative height difference is 1521m.There are steep slopes on both sides of the bank.The gully is in the form of deep V-shaped in general.After the"8.8"earthquake in Jiuzhaigou,the geological disasters are developed in the gully basin,with the amount of loose provenances increased greatly.The static reserve was 61.2×10~4m~3,and the reserve possibly involved in debris flow activity was about 7.34×10~4m~3.Under the condition of rainstorm or continuous rainfall,the debris flow in Wuhuahai was more likely to break out.(2)The gravity of the debris flow is determined to be 1.51t/m~3 through scoring method and engineering analogy method.According to related formulas.the dynamic parameters of debris flow under different frequencies were calculated.The velocities of the debris flow of the frequencies of 20 years,50 years and 100 years are 4.54m/s,5.68m/s and 6.21m/s,and the total flow volume of which are 0.7m3,0.92m3,and 1.1m3.(3)The dynamic simulation software DAN3D was used to simulate the situations of different frequencies debris flow of 20-year,50-year and 100-year.The simulation results show that during the development of debris flow,provenances induced by secmic are transformed to gully provenances,slope provenances and provenances induced by landslides and collapses firstly,then they take part in the activities of debris flow.The provenances induced by landslides and collapses collapses to the front,and then take part in the activities of debris flow,which ars the mian provenances of the debris flow.Under the condition of the frequency of 20-year,the debris flow is deposited in the wide and gentle part of the gully,which can hardly rush out of the gully,and has little impact on the Wuhuahai and its surrounding facilities.Under the condition of the frequency of 50-year,the debris flow will rush out of the gully and flow to the plank road,which will threaten the the plank road and the life and property of tourists.Under the condition of the frequency of 50-year,the debris flow will rush out of the gully with a large number of sediment carried into Wuhuahai,which would cause devastating damage to the landscape of the Wuhuahai and pose a serious threat to the safety of tourists'lives and properties.(4)According to the characteristics of Wuhuahai debris flow and the distribution of its protection objects,the design idea is"source consolidation+bed consolidation+desilting+water filtration".The specific treatments are building two retaining walls in front of the deposits-B1 and B2 to fix them,building five submerged sills to protect the bottom of the steep slope in the circulation area,two desilting dike to block and desilting and four water retaining dikes.At the same time,the original vegetation in the gully area was studied,and the habitat types and original vegetation types in the gully area were summarized.At the same time,according to situation of the habitat,landform,prevention and control purpose and ecological diversity principle of different ecological restoration areas,the ecological restoration plan of clear water area,landslide accumulation area and silt stopping and dike area is determined.