Dynamics of the 2008 earthquake-triggered Wenjiagou Creek rock avalanche, Qingping, Sichuan, China
Dynamics of the 2008 earthquake-triggered Wenjiagou Creek rock avalanche, Qingping, Sichuan, China
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DOI：
10.1016/j.enggeo.2015.12.008
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发表时间：
2016-01
影响因子：
7.4
通讯作者：
Ming Zhang;Yue-ping Yin;M. McSaveney
中科院分区：
文献类型：
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作者：
Ming Zhang;Yue-ping Yin;M. McSaveney
文家沟泥石流是由2008年汶川地震引发的。它行进了4.6公里，在文家沟溪谷留下了1.5 × 108平方米的颗粒状沉积物。通过野外、室内调查和遥感研究，对岩崩动力学进行了研究。动力学过程可分为3个阶段：(1)破坏—由于剧烈岩溶作用削弱的岩体受到巨大的地震地面加速度作用而导致原边坡破坏；(2)落体——岩体因坡度突变经历多次落体，在与地面和山体侧翼的碰撞中破碎成粒状碎片；(3)流动——破碎的颗粒体沿文家沟溪谷流下约3公里。通过对堆积体结构的分析和环剪试验，研究了颗粒状堆积体的输运机理。雨水径流和泥石流在沉积物中切割出一条沟，使沉积物的内部结构得以检查和取样。在剖面上，裸露矿床在靠近基底处最细，向地表逐渐粗化（逆级配）；在纵剖面上，随着移动距离的增加，靠近底部和表面的沉积物都变得更细。在底部附近，颗粒碎屑受到最大的法向应力和剪切应力，破碎成最细的颗粒。晶粒间的法向应力和剪应力均从基部向表面逐渐减小。在环剪装置上对试样进行剪切，模拟颗粒状岩屑内部的剪切过程。颗粒间的剪切阻力随着颗粒的细化而减小，这是颗粒碎屑能够以高速长距离传播的可能机制之一。
The Wenjiagou Creek rock avalanche was triggered by the 2008 Wenchuan earthquake. It traveled 4.6 km and left a granular deposit of 1.5 × 108m3in Wenjiagou Creek valley. The dynamics of the rock avalanche were studied through field and laboratory investigations and remote sensing. The dynamic course was divided into three segments: (1)Failing— the original slope failed due to the huge earthquake ground accelerations acting on a rock mass weakened by severe karstification; (2)Falling— the rock mass experienced several drops due to abrupt changes in slope, and broke into granular debris during collisions with the ground and mountain flanks; and (3)Flow— the broken granular mass flowed approximately 3 km down the valley of Wenjiagou Creek. The transport mechanism of the granular mass of debris was studied by analyzing the structure of the deposit and through ring-shear tests. A gully incised into the deposit by rainfall runoff and debris flows enabled the internal structure of the deposit to be examined and sampled. In cross-section, the exposed deposit was finest near the base, and gradually became coarser towards the surface (inverse grading); in longitudinal section, deposits near the base and on the surface both became finer with increasing travel distance. Near the base, the granular debris experienced the maximum normal and shear stresses, and fragmented into the finest grains. Both normal and shear stresses between the grains gradually decreased from near the base to the surface. Samples were sheared in a ring-shear apparatus to simulate the shearing within the granular debris. Shear resistance between grains was found to decrease as grains became finer due to pervasive fragmentation, which is one of the possible mechanisms by which the granular debris was able to travel a long distance at a high speed.