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汶川地震触发高速远程滑坡–碎屑流堆积反粒序特征及机制分析

ISSN号：1000-6915
期刊名称：岩石力学与工程学报
时间：2012.6
页码：1089-1106
分类：P64[天文地球—地质矿产勘探;天文地球—地质学]
作者机构：[1]西南交通大学地质工程系,四川成都610031
相关基金：国家自然科学基金资助项目（41172260）; 国家重点基础研究发展计划（973）项目（2008CB425801）; 高等学校博士学科点专项科研基金项目（20110184110018）
相关项目：高速远程滑坡-碎屑流“裹气流态化”减阻机理研究

关键词：边坡工程, 高速滑坡, 反粒序, 面积取样法, 筛分分析, 级配分析, 振动筛分, 动力破碎, slope engineering, rock avalanches, inverse grading, area sampling technique, sieve analysis, grain-size analysis, kinematic sieving, dynamic fragmentation

中文摘要：

中国四川汶川地震触发了众多的典型高速远程滑坡–碎屑流。为论证这些高速远程滑坡–碎屑流堆积的层序特征和形成机制,以谢家店子滑坡、牛圈沟滑坡和文家沟滑坡为研究对象,首先对高速远程滑坡运动路径上的竖向分带性进行详细的描述,并根据各带特征,将其划分与命名为气浪影响区、碎屑流跳跃抛洒区、碎屑流流动堆积区、滑动剪切带以及下伏的原沟谷堆积层。在对各竖向分带进行描述的基础上,以碎屑流流动堆积区为重点研究对象,运用面积取样–面积频率法和室内筛分法,对碎屑流流动堆积区不同粒径范围内的颗粒进行详细的粒组分析,并通过质量–频率法的转换,最终获取碎屑流流动堆积区竖向剖面中不同高度层位上碎屑颗粒的累计频率分布曲线,揭示碎屑流堆积体内部所特有的堆积规律——反粒序结构,该结构是高速远程滑坡–碎屑流运动过程及其运动状态的重要反映,是高速滑坡远程运动机制分析所基于的重要地质证据。根据大量的现场调查和室内试验结果,得到以下结论：碎屑流运动路径上因滑面不规则起伏所激励的振动筛分作用和碎屑颗粒之间碰撞所产生的动力破碎作用以及二者的耦合过程应为反粒序形成的主要原因;并基于滑坡运动学与动力学的过程,对上述作用的能量来源和转化过程进行描述。

英文摘要：

The Wenchuan earthquake,which occurred in Sichuan Province,triggered several thousand landslides.For the study of rock avalanche kinematics,the Xiejiadianzi rock avalanche,Niujuangou rock avalanche and Wenjiagou rock avalanche were described to show the geological characteristics of rock avalanches along their sliding paths.According to field investigation,the vertical sorting on the path of rock avalanches is presented;firstly,which is divided into five parts from top to bottom,and named as：the air-blast zone,the leap and air-launch zone of debris,the sliding and deposit zone of debris,the sliping zone,and the original underlying accumulation zone respectively.Then,based on the description of the vertical sorting,the grain-size distribution of the sliding and deposit zones of debris is analyzed by combining an area-by-area technique and sieve analysis,which presents a gradual increase in grain size with height above the base cut quantitatively,proving the existence of inverse grading.This unique inner structure is an important geological evidence for the study of rock avalanche kinematics,which can shed light on the mechanism of their rapid motion.Finally,according to lots of field investigation and test results,one conclusion is proposed that：the kinematic sieving process energized by undulated sliding surface,the dynamic fragmentation process triggered by particle collisions,and their coupling process are the main reasons for the formation of inverse grading;and based on the process of landslide kinematics and dynamics,the above energy sources and transformation processes are described.

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