【摘要】 2004年3月12日，云南省丽江市玉龙雪山南坡发生了较大规模的冰-岩碎屑流型高速远程滑坡。位于斜坡顶部（高程为4 337～5 350m）的岩体和冰川块体沿着高陡岩壁向下滑动，在峡谷地形控制下于干河坝内形成体积约11.2×10~6m~3的滑坡堆积体。本文通过遥感影像分析和现场调查，对干河坝冰-岩碎屑流的地貌与堆积特征进行了详细研究，初步阐释了干河坝冰-岩碎屑流发生的成因机制和运动过程。研究结果表明，节理裂隙发育、源区冻融作用加剧和历史地震效应是此次地震的诱发因素。地形的坡度变化特征、滑体表面“乘船石”结构及内部岩屑的定向排列表明滑坡的运动过程可分为碰撞破碎阶段和扩散堆积阶段。滑坡堆积区广泛分布的“冰川乳坑”和冰水沉积物暗示堆积体底部松散沉积物减阻或是干河坝冰-岩碎屑流具有远程效应的有利因素。深入理解干河坝冰-岩碎屑流的地貌特征及运动学过程，对揭示高速远程滑坡的超强运动机理具有重要的理论意义，同时对我国西部高寒山区大型滑坡灾害的预测预警亦具有现实意义。更多还原

【Abstract】 On March 12,2004,a large-scale rock-ice avalanche occurred on the south side of Yulong Snow Mountain in Lijiang,Yunnan Province. The slide body consists of the upper ice mass and the lower rock mass,with a total volume of 9.1×10~6m~3. The maximum high drop of the landslide is 1 971m,the longest movement distance is 4 860m,and the apparent friction coefficient(H/L)is0.40. The rock-ice avalanche with the volume of 11.2×106m3and the movement length of3 170m developed in Ganheba. This paper presents a detailed study of topographic and geomorphological characteristics through remote sensing images and field investigation.The lithology of the study area consists mainly of limestone with two sets of structural faces. Although seismic activity data indicate that the occurrence of the Ganheba rock-ice avalanche is not directly related to earthquakes. The Yulong Snow Mountain is tectonically active,and historical earthquakes likely caused structural damage to bedrock along the joint surface in the source area. Besides,the temperature in the Lijiang area showed an increasing trend from1951to2005. Yanggongjiang No.5Glacier near the study area decreased dramatically. The long-term freeze-thaw cycling is likely to aggravate the rock damage in the source area. Therefore,the triggering factors of the Ganheba rock-ice avalanche are highly fractured limestone,freeze-thaw cycle,and historical seismicity.According to the topographic and geomorphological characteristics,the Ganheba rock-ice avalanche can be divided into three zones:the source area,the circulation zone,and the accumulation zone. The slope in the source area is significantly steep,and the average slope angle is48°. There are two groups of structural planes developed in the bedrock. A small number of debris remains at the platform in the circulation zone. The ice mass is mainly distributed in the accumulation area Ⅲ-1,while the surface of the accumulation area Ⅲ-2is widely distributed with glacial milk pits and a unique“boat rock”structure. The directional arrangement of boulders can also be observed in this section. The movement process of landslides can be divided into two stages:the precollisional fragmentation stage and the post-spreading accumulation stage. In the first stage,the destabilized rock body is violently broken by a high-speed impact on the platform. In the second stage,the debris flow moves as a flexible sheet with all displacement taking place in the fluvioglacial deposit and the inter-particle fragmentation is not significant.Based on the above analysis,we believe that the emplacement process of the Ganheba rock-ice avalanche is as follows:(1)The bedrock joint of the permafrost area tended to expand under the freezing and thawing cycle.Until March2003,glacial snowmelt water in the fissure led to a decrease in basal friction and the effective stress in the bedrock,which eventually caused sliding damage along the structural surface of the limestone.(2)The overlying ice mass and underlying rock mass formed a double-layer sliding structure. They collided with platform at the circulation area,and was significantly broken under the control of the structural surface of the bedrock.(3)The ice mass stopped in the accumulation area Ⅲ-1 and formed several arcuate lateral ridges within a few years. Constrained by the topography,the debris flow in the accumulation zone Ⅲ-2 first extends toward SE120°,and then turns to NE85° with the valley shape.(4)After the valley turns,the velocity of the debris flow drops abruptly and the thickness of the deposit gradually becomes thinner,forming a unique“boat rock”structure.An in-depth study of the geomorphic features and kinematic processes of the Ganheba rock-ice avalanche is of great significance to revealing the kinematic mechanism of high-speed remote landslides. It is also of importance to the prediction and early warning of large-scale landslide disasters in alpine mountains of western China.更多还原