Research On The Calculation Methods Of Debris Flow Hazard Affection Parameters And Relevant Optimizations Of Countermeasure Design Along Highway At Active Fault Zone

After the devastating Ms8.0earthquake of Wenchuan area occured in May.12.2008, the debris flows along Ya’an to Lugu highway, whose activities had been tremendous influenced by the active faults in the area, were getting more and more active and destructive. For now, due to the neglection of the influence from active faults and earthquake in the current domestic standards, the scales of these debris flows were often underestimated, which made the countermeasure unreliable. Supported by the National West Traffic Construction Science and Technology Item "Study on the technology popularization and application of debris flow hazard mitigation along highway in active fault zone (No.200831800087)" and the Graduate degree thesis Innovation Foundation of Central South University "Study on the Key technique of Debris Flow Mitigation and Prevention Work Design and Optimization Based on the Hazard-affected Mechanism (No.2011SSXT160)", based on the debris flow mitigation programs along the high way, this dissertation was supposed to discuss a series of calculate methods for debris flow hazard parameters in the active fault zone after the earthquake, and then to propose optimization methods for drainage canal design and gravity-dam structure. The main work and achievement of this dissertation is as follows:(1) Based on the field investigation of19debris flow gullies along the YaLu highway, the affecting factors of debris flow development and activity characteristics were analyzed. And the position distribution feature of these debris flow gullies was studies with the SRTM space data from CAS, thus the affect mechanism of debris flow development and activity was revealed based on the position relationship between the debris flow gullies and the active faults;(2) Based on the summary of the present achievements on the debris flow forming condition and activity feature, the analysis methods for development and evolution characteristics of debris flow after earthquake were proposed, thus the development trend of debris flow along YaLu highway was preliminary predicted especially focused on the period after the Wenchuan Ms8.0earthquake, which indicated that the debris flow after earthquake in this area would be generally characterized by its scale-increasement and needed to be further mitigated.(3) A series of calculate methods for debris flow hazard scale parameters were proposed based on the analysis of debris flow activity characteristic after the earthquake, including:the modifier formulas to calculate the maximal discharge and total amount of the debris flow after the earthquake, the integrity coefficient of gully morphology based calculate method to the bulk density of debris flow at active fault zone, and the calculate method to the lateral distribution features of debris flow velocity and impact. The effects of all the methods proposed above were aslo verified by the engineering instance analysis;(4) The initiative mitigation issue based debris flow hazard countermeasures were summarized. And the common problems encountered in the drainage canals and dams were also discussed and analyzed, thus the optimization methods for debris flow countermeasures were proposed, including:the anti-silting design method of debris flow drainage canal and structure optimization method of debris flow gravity-dam. All the optimization methods proposed above were then verified by the application instances to be of highly economic value and great mitigate effect.