青藏高原古高速远程滑坡沉积学特征研究

高速远程滑坡运动学机理是国际工程地质领域亟待解决的重大前沿性关键科学问题.为探索高速远程滑坡的运动学机理,以青藏高原不同构造背景下的三大高速远程滑坡为研究对象,通过现场工程地质调查与分析,详细探讨了滑坡运动路径上所揭露出的各种表面与剖面沉积学特征,结果显示:(1)沿滑坡运动路径上依次可见大型堆积平台、纵向脊、横向脊、堆...

Observations on the sedimentary structure of prehistoric rock avalanches on the Tibetan Plateau,China

Rock avalanche kinematics is a forefront major challenge in the field of engineering geology globally. To explore the kinematics of rock avalanches, three typical prehistoric cases occurring on the Tibetan Plateau were investigated in this study. Detailed field surveys and analyses of their surface and internal sedimentary structures revealed the following: (1) Obvious sequential distributions of toreva blocks, longitudinal/transverse ridges, and hummocks were observed, and the rock avalanches could be divided into three zones from rear to front: the source area, transition zone, and accumulation zone, according to the spatial distribution of these landforms. (2) Inverse grading was observed in the deposits, with tree facies, carapace facies, body facies, and basal facies, divided vertically from top to bottom. In the carapace and body facies distribute retained stratigraphic sequences, jigsaw structures, etc.; in the basal facies, diapiric structures, convoluted laminations, etc. can be observed, indicating an intensive interaction between the basal facies and substrate. Based on these observations, we propose a plausible mechanism for the emplancement and accumulation of rock avalanches as follows: As avalanche mass became detached from the source area, it underwent first a rapid laminar flow-like motion, then an extensional sliding motion in the transition zone, followed by an extensional sliding motion as it arrived at the accumulation zone; and if the water content of the substrate were high, a rapid radial spreading process could occur at its frontal edge due to the rapid decrease in basal friction.