Study On Startup Mode Of Slope Material Sources And Dynamic Reserves Prediction Of Qipan Gully Debris Flow In Wenchuan County

Debris flow, a kind of geological hazards, occurs frequently and does tremendous harm in the mountains. The material source is the basic condition of debris flow that determines the size of debris flow, which also plays a decisive role in the treatment engineering of debris flow. More than half of the material sources of debris flow are slope material sources, the formation and startup mode of which are complex and it is difficult to calculate dynamic reserves. This thesis, based on the Qipan Gully in Wenchuan County, studied the types and startup modes of slope material source, and then proposed the calculation method of dynamic reserves. The influence factors of dynamic reserves were also given. The main research contents and results are presented as follows:(1)By analyzing the loose solid materials in Qipan Gully, the slope material sources were divided into four types, including collapse deposits, landslide deposits, overland deposits, and seismic sources on slope crest. The characteristic of each type of slope material source was analyzed respectively.(2)Based on the classification of the slope material sources, each kind of startup mode of slope material source was analyzed in detail.The startup modes of collapse and landslide deposits were divided into three categories based on different locations.(3)The scour mechanisms of debris flow were analyzed and the formula of maximum scour depth of debris flow was deduced. On the basis of the scour mechanisms, two kinds of calculation methods of dynamic reserves of the collapse and landslide deposits were given:1) searching circular sliding surface method,2) the stable angle method. In the stable angle method, the rupture angle formulas were derived independently by the coulomb theory and by the limit equilibrium theory.(4)For overland deposits, Revised Universal Soil Loss Equation (RUSLE) was cited to calculate dynamic reserves. The calculation methods of five factors of RUSLE were given, including rainfall erosivity factor, soil erodability factor, slope length and steepness factor, cover management factor, and conservation practice factor. The instance of the slope material source point P5 was demonstrated based on RUSCLE.(5)The method of calculating the amount of seismic source on slope crest was given by using geometric analysis method. It was verified through numerical analysis with FLAC3D.(6)Eleven influencing factors of dynamic reserves were analyzed with analytic hierarchy process (AHP). It is further divided into three levels:tremendous influence(> 10%), large influence(> 5%), general influence(< 5%), based on their weighted values.