Some Key Problems on Debris Flow in Wenchuan Earthquake Area
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摘要: 为解决2008年512汶川地震后,在地震灾区大部分泥石流沟实施的拦砂坝、排导槽等首期治理工程效果不佳、部分工程甚至失效的问题,根据松散物源启动量估算明显偏小、拦砂坝设计库容不够、排导槽过流断面偏小的状况,分析了地震灾区泥石流形成特点和暴发规律,针对持续性、大规模和群发性方面的估计不足,系统地进行了经验总结.通过2010和2013年两次特大型泥石流的勘查、设计和治理工程实践表明:震区泥石流在启动机理、堵塞溃决、持续时间、冲出规模等方面与一般泥石流相比存在很大区别,总结出以下经验: (1) 合理确定泥石流堵溃系数及相应流量;(2) 针对不同类型泥石流及保护对象提出有效的治理工程方案,例如拦挡、固坡、排导、停淤方法的合理组合和有效利用;(3) 合理分配拦砂坝的有效高度及数量;(4) 合理选用坝体结构类型,例如实体坝、缝隙坝和梳齿坝.上述经验在绵竹县清平文家沟、汶川县红椿沟、七盘沟、桃关沟和宝兴县冷木沟特大型泥石流的勘查、设计及治理工程中进行了充分的应用验证,并取得了成功.Abstract: After the Wenchuan earthquake on May 12, 2008, some initial treatments, such as silt dams and drainage ditches which were built in debris flow gullies in the earthquake area for debris control, showed a poor performance and went into a failure condition because of the underestimated launch quantity of loose material resource, the insufficient design capacity of the silt dams, and the small cross sections of drainage grooves. To deal with these problems, the formation characteristics and outbreak regularities of debris flow in the earthquake area were analyzed, and a systematic summary of experience was obtained from the lesson of insufficient understanding of the continuous, massive, and group-occurring of the debris flow. There are some significant differences between the earthquake debris flow and general debris flow in the starting mechanism, block and break, lasting time and break-out quantity of loose materials, and so on. Through the engineering practices in exploration, design and management of two giant debris flow in 2010 and 2013, some experiences are summarized as follows: (1) reasonably determine the blocking collapse coefficient and the discharge of debris flow; (2) put forward effective treatment plans according to different types of debris flows and the preserved objects; for example, effectively combine the block, slope reinforcement, drainage ditches and silting field; (3) reasonably distribute the effective height and number of silt dams; and, (4) choose reasonable structure types for dams, such as entity dam, crack dam and comb dam. The above experience has been successfully applied and verified effective in the investigation, design and management projects of large debris flows in Wenjiagou gully in Qingping town of Mianzhu County, Hongchungou gully, Qipangou gully and Taoguangou gully in Wenchuan County, and Lenmugou gully in Baoxing County.
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Key words:
- earthquake regions /
- debris flow /
- management /
- blocking collapse coefficient
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