东河口滑坡-碎屑流高速远程运移机制探讨

DISCUSSION ON LONG RUN-OUT SLIDING MECHANISM OF DONGHEKOU LANDSLIDE-DEBRIS FLOW

青川东河口滑坡-碎屑流是"5.12"汶川大地震触发的典型高速远程滑坡,滑坡自高程1300m处开始滑动,总滑程约2400m,致使780余人遇难。野外调研结果表明,该滑坡自启动到最终静止,分别经历了滑坡启动阶段、重力加速阶段、圈闭气垫效应飞行阶段、撞击折返阶段及长距离滑动堆积阶段5个重要动力过程,最终抵达下寺河左岸的红花地村并形成堰塞湖。文中通过对该高速远程滑坡-碎屑流的地质背景及形态特征进行剖析认为,东河口滑坡启动区的断层破碎带、局部凸起地形以及力学性质较差的千枚岩、板岩的存在,对该滑坡的启动均有着显著影响;滑坡体在运行一段距离后是否可以继续保持高速远程滑动,除了有利的地形外,滑体滑动路径上高含水量的溪流堆积物的存在,是促使该滑坡成为高速远程滑坡-碎屑流的重要原因之一。

The Donghekou landslide-debris flow is a typical rapid long run-out landslide triggered by the great Wenchuan earthquake. It started from the elevation of 1300m and caused 780 deaths, with a total long run-out of 2400m. Field investigations show that, during the sliding process from start-up to stop, this landslide-debris flow experienced the following five dynamical stages, such as the starting-up stage, the gravity speed-up stage, the enclosure air cushion effect stage, the impact reentry stage and the long run-out sliding accumulation stage. Finally, it reached the Honghuadi village, which is located at the left bank of the Xiasihe River, and the dammed lakes occurred. By analyzing the geological setting and feature of this landslide-debris flow, we can draw a conclusion that the initiation of Donghekou landslide-debris flow is mainly affected by the fault crush belt, the local convex landform and the phyllite and carbon slate with weak mechanical property; for the rapid and long run-out sliding of this landslide-debris flow, the water containing condition of the slope debris on sliding route is an important factor besides the advantage landform.