青海大通县韩家山滑坡是西宁盆地最危险性的滑坡之一。为分析该滑坡的形成机制，论文基于高精度的地形数据开展变形形式、平面堆积特征的调查；结合连续取芯钻探数据，重建了滑体结构；为定量获得滑动带力学性质的变化过程，进行了滑体与原岩物质成分、水理性质、应力应变性质的物理化学测试，讨论了多级滑动剪切面的形成机制。分析表明：(1)滑体内不存在软弱地层，为近似均质地层。滑体为单一的新近系红色泥岩夹石膏层，不具层理，不含大于0.25 mm碎屑颗粒。泥岩内粘土矿物含量在29.7%~46.3%之间，碳酸钙含量在9.84%~11.58%之间。岩体内含形态不一、大小不一的石膏结核；(2)泥岩粘粒含量高，水敏性与粘滞性强。泥岩干燥饱和吸水率最低为26.31%，最高为42.12%。泥岩样品环剪试验呈应变软化型，随着含水率的增大，强度急剧降低。滑体快速滑动过程中，非饱和的滑带土受粘性物质、孔隙性的影响，产生强吸力；(3)滑体以旋转变形破坏为主，斜坡受河流侧向侵蚀影响，滑床附近的岩土体渐进性破坏，出现多级滑动现象。%There are 31 large-scale landslides in Xining Basin of Qinghai Province, and the Hanjiashan landslide in Datong County is one of the most dangerous. To analyze the deformation mechanism of that landslide, this paper described geometric and kinematic characteristics of the landslide and reconstructed the structure based on high-precision topographic data and continuous coring boreholes data. The authors conducted physical and chemical tests of the material composition, water-physical property and stress-strain property of the shear zone, described the process of mechanical property of shear zone on the basis of these quantitative tests, and then discussed the formation mechanism of multilevel rotational shear planes. Some conclusions have been reached: (1) there is no soft strata in slide mass; instead, the strata seem to be homogeneous formation. The slide mass is composed of red mudstone intercalated with gypsum horizon of Neogene, and both the gypsum and red mudstone are not in stratification and have no particles whose diameter is over 0.25 mm. The clay mineral content of the mudstone is 29.7%~46.3%, and the CaCO3 content is 9.84%~11.58%. The concretion of gypsum in the rock mass with different forms and dimensions may not have been formed by salt lake sediments; (2) the mudstone has high clay content, strong water sensitivity and viscosity. The lowest dry saturated water absorption is 26.31% and the highest is 42.12%. In ring shear test, the mudstone became strain softening, and the strength rapidly decreased when the moisture content increased. When the mudstone was in fast slide, the unsaturated slide zone could have strong suction due to the influence of sticky substances and porosity; (3) the mudstone of the slide mass was mainly in rotational deformation and the multilevel slide zone might have resulted from progressive damage of rock and earth mass and was probably influenced by lateral erosion of the river. Under the influence of lateral erosion of the river, the stress changed and concentrated at the foot of the slope, and the side stress of the adjacent rock mass which changed and concentrated by the fist slide would tend to cause the large-scale slide and progressive failure.
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