| Post-fire debris flow disasters is a very special phenomenon, It refers to after forest fire, the frequency of debris flow will increase in the ravine. There was a forest fire in Mount YuanGen,Zhengdou village, Xiangcheng county, Sichuan Province of China On 1 June 2014 at 1840.After 4 days of tough break,the forest fire basically put out on June 5th10 am. Then, influenced by local heavy rainfall, two catastrophic debris flow disasters occurred in the Reneyong Ravine in June 8, 2014 and August 24, 2015 respectively.It not only caused huge economic loss, also a serious threat to the life property safety of the local residents. This paper takes the Reneyong Ravine debris flow as the research object, at the early stage of the collect related geological data and survey data on the basis of detailed investigation for the debris flow in the studied area, including the burns, debris flow provenance,the channel condition and development history, and then analyzed the natural geographical conditions and development characteristics of the Reneyong Ravine debris flow and the effect of forest fire on debris flow and simulation of the post-fire debris flow by artificial simulation of rainfall device in the indoor. Finally on the basis of this study, research on the cause of the Reneyong ravine debris flow mechanism preliminary exploration. In this paper, the main research work and achievements are as follows:(1) By collecting a large number of hydrology, meteorology and regional geological data, combined with field investigation, analyses the debris flow of Reneyong revine formation conditions and explain the regional geological environment conditions conducive to the formation and development of post fire debris flow.(2) Detailed investigation of the burns of the upper reaches of the Reneyong ravine Mount Yuangenshan, and emphatically from the fire damage to vegetation, soil physical properties, microstructure and mechanical properties of these four aspects to analyze the effect of forest fire on debris flow disaster.(3) Build the indoor artificial rainfall simulation test device, respectively constructed by unburned soil and burned soil slope were artificial rainfall experiment, and then through comparing analysis of two groups of test the forming process of slope debris flow, and reveals the formation process of debris flow after the fire.(4) Based on the experiment of artificial rainfall model test, the change law of water content and pore water pressure of the different soil in the antecedent rainfall condition was compared and analyzed. No matter for non burned soil or burned soil slope, different periods of surface soil and deep soil the water content is different, because the water infiltration and evaporation requires a certain amount of time. But the change trend of pore water pressure in different soil has been quite large. For the burned soil, the infiltration stage is relatively disordered, which shows that the permeability of the soil after the fire has changed significantly. Finally, comparative analysis the interaction of short duration heavy rainfall and surface runoff slope local saturation stage and creep slip stage, slipstream and sedimentary phases as the test of the change process.(5) The formation of debris flow in the Reneyong Ravine is the result of the combined action of forest fire and heavy rainfall, which can be summarized as two aspects: the forest fires and sediment source and the continuous rainfall and the water source. Forest fires affect debris flow provenance conditions.After forest fire, burns slope loose sediment and a large number of ash is an important source of the post fire debris flow in the Reneyong Ravine. Forest fire changes the threshold of rainfall for debris flow,after forest fire, the amount of rainfall,rainfall intensity and hydrodynamic conditions of the debris flow were significantly decreased. In addition, after the forest fire the ash composition can promote the occurrence of debris flow. |
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