摘要:
平推式滑移是西宁—民和新近纪盆地内巨型滑坡的主要运动形式之一, 互助县菜子沟大型滑坡持续变形, 威胁350多位村民的安全, 致灾风险较高.论文基于滑体地貌形态、岩性组合特征与变形破坏过程的勘查, 系统分析了控滑岩层的物质组成、水理特性与力学性质, 探讨了新近纪泥岩结构、强度的耦合变化机理,进而解析了滑坡的平推运动机制, 初步研究表明: (1)近水平的新近纪泥岩为菜子沟滑坡内的控滑岩层, 古浪地震触发该滑坡沿着25 cm 厚的软弱层出现首次平动, 近期的变形受到汛期雨水入渗、远场地震动的影响;(2)西宁盆地新近纪泥岩为黏土岩, 黏粒含量在21.84%~51.44%之间, 滑带的形成是剪切局部化作用的结果,其渐进扩展受物质结构、应力环境与力学响应机制的控制, 滑带选择黏粒含量高、碳酸钙的含量低、胶结力低位置扩展, 其黏粒含量为63%~68%, 碳酸钙含量为5.27%~4.12%, 内摩擦角在6.8°; (3)菜子沟滑坡处于干旱地区, 极端强降雨天气较少, 地震惯性滑移和地下水的浸润作用、水解作用是滑坡现今蠕变变形的主要诱发因素, 该过程还将持续.
Abstract:
Translational sliding is one of the major movement types of large landslide in Xining–Minhe Basin of Qinghai Province. The on-going deformation of the large landslide at Caizigou, Huzhu County, Qinghai is threatening the lives of over 350 villagers with its relatively high risk of disasters. In this paper, the authors systematically analyzed the material composition, hydraulic characteristics and mechanical property of the strata of the gliding mass, and discussed the coordinated changing process between the Neogene mudstone structure and mechanical process to further explain the translational movement mechanism of the landslide. Some preliminary conclusions have been reached: (1) Gulang earthquake triggered the first translation of the slide against a weak layer of 25 cm thickness. The recent deformation was influenced both by infiltration of rain water during the flood season and the earthquake. The flatly inclined Neogene mudstone served as the control stratum of Caizigou landslide. (2) The Neogene mudstone of Xining Basin is clay rock with a clay content between 21.84% and 51.44%. The formation of the sliding belt resulted from shear localization, whose gradual expansion was controlled by substance structure, stress environment and mechanical response mechanism. The sliding belt tended to expand at the positions with higher content of clay, lower content of calcium carbonate and less cementing force, where the clay content is between 63% and 68%, the calcium carbonate content is between 5.27% and 4.12%, and the angle of internal friction is 6.8°. (3) Caizigou landslide is located in an arid area with seldom extreme heavy rainfall, so the earthquake and underground water infiltration and hydrolysis seem to be the major contributors for the present creep deformation, and this process is likely to continue.
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