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Li J.,Gansu Institute of Geological Environment Monitoring | Li R.-D.,Gansu Institute of Geological Environment Monitoring | Qu J.-X.,Gansu Institute of Geological Environment Monitoring | Zeng Y.,Gansu Institute of Geological Environment Monitoring
Northwestern Geology | Year: 2011

Before, the debris flow risk assessment only focuses on a specific time point's risk. Few study analyzed the assessment factors changes and the risk's variations as a result of time change (before or after the debris flow occurring) . The paper took Zhouqu Sanyanyu debris flow as a study case, applied the single debris flow risk assessing model; utilized the data of reconnaissance, explorations, and count measures engineering designs; analyzed the risk assessment factors changes at different time points which are before "8. 8" disasters, at present, and after count measurements; acquired the parameters of hazards and vulnerability separately; and calculated the risks at these three time points. Finally, discussed the risks assessment results and analyzed the detailed reasons for the risk's variations at different time points. Source

Wei J.,Gansu Institute of Geological Environment Monitoring | He S.-J.,Gansu Institute of Geological Environment Monitoring | Sun X.,Gansu Institute of Geological Environment Monitoring
Northwestern Geology | Year: 2011

Zhouqu "8. 8" Sanyanyu debris flow is a typical disaster occurred at deep valleys with high and steep rock side slopes in south of Gansu Province. How to mitigate the risk of this kind of debris flow is a subject valuable to research on. This thesis summarized the principles and methods that mitigate the debris flow on the basis of risk-reducing ideas. It analyzed the practical problems that the Zhouqu debris flow mitigations have to face, which includes the limited environmental capacity, the difficulties to relocate the town, and the psychology of local people after this catastrophe. Thinking of these practical problems, the author proposed the comprehensive mitigations which are partial evacuation plus engineering countermeasures plus monitoring & early warning plus education for local resident, and made a relevant detailed explain for each of mitigation measurements. Source

Zhao C.,Gansu Institute of Geological Environment Monitoring | Hu X.-D.,Gansu Institute of Geological Environment Monitoring
Northwestern Geology | Year: 2011

The extra large debris flow in Zhouqu county on August 8, 2010 caused serious disaster which causing widespread concern of domestic and international engineering geological community. The investigation after disaster found that the former prevention and control projects were completely destroyed and the protection ability was breakdown. We should rethink it in order to learn this painful lesson. Based on the field investigation, through the discrete element simulation and theoretical analysis, the paper obtains some conclusions, such as the block dams are not strong enough against the stamping force of debris flow, the flow of the drainage projects does not match the cross-section, the flood discharge capacity is serious insufficient, there are too much curved conduits and the curvature is too big. Consideration and awareness of these issues will provide reference for the treatment scheme after the disaster. Source

Li Z.-H.,Gansu Institute of Geological Environment Monitoring | Zhao C.,Gansu Institute of Geological Environment Monitoring
Northwestern Geology | Year: 2011

Bailong river basin is located in the sharp slope deformation zone of Qinghai-Tibet Plateau transition to Loess Plateau, and it's one of the most serious debris flow and landslide hazards region in our country. The "8. 8" debris flow's occurrence in Zhouqu county exposed the extent of the geological hazards research is low, the forecasting and warning capacity is low, the risk mitigation measures is inadequate. In order to avoid similar serious geological hazards, we should further strengthen the basis of investigation and research work. The ideas of further exploration: firstly, carry out a comprehensive investigation on Diebu, Zhouqu, Dangchang, Wudu, Wenxian, Kangxian county accordance with the "specification of investigation for landslide, collapse and debris flow (1: 50000)" requirements. Secondly, carry out one by one investigation for the potential points which threat county, town and major settlements accordance with the requirements of accuracy of pre-survey planning. Thirdly, carry out monographic research on the different geological hazard formation mechanism, disaster mode, monitoring and early warning, risk mitigation measures and other issues. Source

Wei X.-P.,Gansu Institute of Geological Environment Monitoring | Bi Y.-H.,Gansu Institute of Geological Environment Monitoring
Northwestern Geology | Year: 2011

The terrain and topographical characteristics loosening solid matter characteristics and rainfall characteristics as well as statics and dynamic characteristics of giant debris flow were obtained by field investigation and analysis on the debris flow hydrodynamic force conditions based on platform of ArcGIS and using DEM. The results show that the terrain and topographical can provide favorable condition for formation and running of runoff. The amount of loosening solid matter is so great that amplify dam. The severe local weather process with heavy precipitation short duration is the main cause for this massive mudslide. The bulk density of debris flow is 2.10 t/m3, is high density viscous debris flows, and yield stress is over 8 000Pa, the velocity of dayanyu xiaoyanyu (rainfall confluence area) and sanyanyu (debris flow accumulation area) is respectively 8. 97 m/s, 7. 06 m/s, 6. 02 m/s, the maximum flow is 1 659 m3/s, 1 553 m3/s, 1 896 m 3/s, the impact force is 46 676 tf, 40 236 tf and 21 182 tf, so the destructive power is great and its damage is serious. The great destructive of debris flow in circulation terrain is mainly down cutting erosion, affected by the terrain, the impact force is decreased and the debris flow stacked. Source

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