Reserch On The Developing Characteristics And Pridiction For Hazardous Zone Of Jiangkou Debris Flow In Danba

As one of the common geological hazardouss in mountain area, debris flow threatens human lives and belongings seriously due to its sudden out-breaking and rapid flowing. Despite that debris flow sediment and flood in the accumulation fan, many towns in mountain area are locate there for the sake of its flat terrain, this takes quite a lot of potential problems for the occurrence of debris flow disasters. Southwestern China has witnessed a number of large scale debris flows in recent years (For example Wenjia gully, Hongchun gully and Qipan gully debris flows which occurred in Wenchuan, Beichuan and Mianzhu between 2009 and 2013). Due to the shortage of forecast for hazardous zone, these debris flow disasters not only destroyed the reconstructed buildings but also caused significant damages to people’s lives and properties.Generally, the hazardous zone of debris flow was predicted by empirical formulas or mathematical models which based on statistics at home and abroad, but the forecasted hazardous zones often vary greatly with the realities. Therefore, it is urgent and meaningful to explore an objective and credible technology to predict the hazardous zone of debris flow. The numerical simulation technology of debris flow can not only reproduce the development process of these disasters, but also predict them in order to provide an appropriate design for countermeasures of disasters, therefore it began to attract the attention of scholars in recent years.Firstly, the developing characteristics of Jiangkou gully were studied from the regional geological conditions and forming conditions by field survey and mapping. Then the dynamic characteristic parameters of the debris flow were calculated. Finally, a general computational fluid dynamics software—CFX was introduced into the prediction of hazardous zone of debris flow, and then the hazardous zone of Jiangkou gully was analyzed by three-dimensional flow numerical simulations before and after its prevention. The results of the article are as follows:(1) The regional geology of the study area was described, and the requirements of forming conditions of Jiangkou debris flow was analyzed by three aspects—the terrain condition, the loose material condition and the water condition. The motion parameters of debris flow was determined through the rain-flood method, then the history and the break out frequency of the debris flow was invested and analyzed in detail.(2) A three-dimensional fluid model of the accumulation fan of Jiangkou debris flow was established, and a numerical simulation combining with the Bingham rheological model was analyzed using the software of CFX which based on finite volume method, then the inundation process and the hazardous zone in the accumulation fan were obtained precisely.(3) Proposed the comprehensive countermeasures which combining with check dam, dike and drainage canal. The inundation process and the hazardous zone of the debris flow was also analyzed after the countermeasures was added into the model, and the result of the simulation proved the feasibility of the countermeasures.The numerical simulation technology of debris flow based on CFX can avoid the subjective factors that may affect the prediction of hazardous zone and the precise hazardous zone can be obtained, it can also provide guidance for the design of countermeasures for debris flow. If expand researches could be took on the areas that threatened by debris flow in southwestern China by this method, it should be useful in the field of construction site choosing and railway line selection, so that the risk of debris flow could be reduce.