2017年“8·8”九寨沟地震对景区泥石流治理工程影响机制研究

Study on the damage of the August 8,2017 Jiuzhaigou earthquake to debris flow mitigation engineering in the national park

为了研究2017年"8·8"九寨沟地震对景区泥石流治理工程的影响,利用野外调查、采样测试和对比分析等手段,基于泥石流治理工程损毁的时序、分布及表观特征,分析工程震损类型和机制,提出防治建议和修复对策。结果表明:(1)单体治理工程震损程度分为完好、轻微、较重、严重和损毁5级,占比分别为30%,43%,12%,9%和6%,单沟治理体系震损程度可分为系统性损毁、局部损毁和轻微损毁,占比分别为4.76%,57.14%和38.10%;(2)基于震损与地震的相对时序关系,有直接震害和震后间接损毁2种方式,前者包括震裂破坏和同震灾害破坏,主要受地形条件和工程结构尺寸约束,后者有冲击破坏、磨蚀破坏、绕流破坏等,主要受控于灾害物理特性和动力特征的演化;(3)地震影响最大的间接损毁是多要素耦合作用结果,具有"多因同症"的特点,主要驱动力为流量、流速、容重和漂木含量;(4)震后泥石流治理中,需适当增大动力参数,优化关键结构,预留安全储备,损毁工程的修复需同时满足最小地表扰动和景观保护需求,可采取非开挖加固和功能改造等手段。

A magnitude Ms 7.0 earthquake struck the Jiuzhaigou World Natural Heritage Park,in Sichuan province,Southwest of China on August 8,2017,and trigged abundant coseismic landslides in the scenic spot. Due to 3 strong rainfalls,dozens of debris flow hazards occurred in the national park after the earthquake. Field survey,sampling test and comparative analysis were used to research the damage models of the debris flow mitigation engineering completed from 1984 to 2016. In total,there are 11 mitigation systems of debris flow gully suffering from partial damage such as Keze gully,Rize 1 st gully,Rize 2 nd gully and Shuzheng gully,and the engineering of Xuan gully near the Xiajijie lake. Striking of the earthquake the mitigation engineering would trigger a coseismic damage,mainly affected by topographic conditions and engineering structures. As the formed conditions changed,it also caused an indirect damage by increase the value of the charismatics of debris flow. The indirect damage,which has the characteristics of "multi-pathogenesis and same symptoms",is controlled by the physical and dynamic characteristics of debris flows. Besides,the charismatics values of discharge and density,the driftwood of debris flow are other important factors to the engineering damage. When encountering a larger hazard than the standard of initial design,the mitigation engineering will cause 7 types of damages such as the impact,the abrasion,the erosion,and the damage due to flow direction change. It is suggested that the effects of discharge amplification and driftwood should be focused on for reconstructing the mitigation engineering of the national park after the earthquake.