| Debris flow is one of common type of geologic hazard, which is widely distributed in southwest and northwest of China. The outbreak of debris flow is sudden, the duration is short, but it causes very serious disaster.Shangzhuo gully debris flow,which is located in Zhuoni coutry of Gansu Province,is a high frequency viscous debris flow.Based on the analysis of formation conditions,the author found that the debris flow is formed with plenty of solid loose mass which were caused by the influence of gravity and erosion of the steep mountain channel.This type of debris flow is quite typical in this area.The article took Shangzhuo gully debris flow as research object,mainly analyzed its formation mechanism,proposed the corresponding comprehensive preventing and controlling measures. Calculation through mathematical model and numerical simulation methods assessed the risk and calculated the stress and the deformation of the z-direction,that provided theoretical basis for the above mentioned measures.The research contents and main results of the article are as follows:First,based on research results of many reference books and field research, the article piled up the orgination of the textural preperties of Shangzhuo debris flow, the landform characteristic as well as distribution of river basins and so on looked into the whole process of its formation, movement and accumulation and concluded the features of the flow,namely the debris flow forms with unconsolidated material on a hillslop when the material becomes satureted and unstable,the debris flow tend to follow steep maintain channels with a lot of collapse and rich sediments.The author is unable to distinguish between forming and passing area of Shangzhuo debris flow.Secondly, based on the detailed analysis of formation mechanism, combined with Shangzhuo debris flow’s development history, the article extracted Shangzhuo debris flow risk impact factor, the weight of the impact factor obtained through the analytic hierarchy process.For Shangzhuo debris flow, maximum volumes of material delivered by single events、the maximum1h rainfall、main gully average gradient, the solid loose mass reserves are major factors that affect the formation and decide damage degree, the weight for them were0.2589,0.1957,0.1547and0.1321.The author than set up the mathematical model for risk assessment based on the major factors, calculated out the value was0.45and came to conclusion that the risk of Shangzhuo debris flow is at medium.According to the risk assessment for Shangzhuo debris flow, the author selected the defence standard,investigated the status of the original projects, proposed the comprehensive management, which aims to fully utilize the existing engineering, reinforce them, and build the drainage projects in the city. Finally, the author designed the dam structure in the main channel, after checking the structure is stable. Then take software as a platform for the numerical simulation, established the finite element model to calculate the distribution of displacement and stress of the dam, simulated the variation characteristics of the pressure impact on the landslid dam under different slope ratio of upstream face(1:0.35,1:0.3,1:0.2) and obtained the best slope ratio of upstream face was1:0.35. Under this condition, the maximum displacement,tensile stress and compressive stress were relatively small,and the distribution curve of the displacement and stress were more reasonable.Through the analysis of the causes of the debris flow, eigenvalue calculation, risk assessment and so on, the understanding of the debris flow mechanisms and the injurious feature have been strengthened further. After simulating the dam, the structure of the dam was optimized,the safety and the rationality were improved.lt can provided the basis and the reference for the next optimization design. |
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