青海高原龙穆尔沟红层滑坡变形机制的地质分析与模型试验研究

GEOLOGICAL ANALYSIS AND MODEL EXPERIMENTAL STUDY OF DEFORMATION MECHANISM OF DITCH-MOORE RED BED LANDSLIDE AT QINGHAI PLATEAU

以西久公路(S101线)龙穆尔沟DH6#红层滑坡为典型代表,采用地质分析与室内模型试验相结合的方法,对河谷下切和雨水浸润作用下青海高原红层滑坡的变形破坏过程进行研究。在地质力学模型试验中,以坡体开挖来模拟河谷下切卸荷作用,采用均匀毛细浸润技术模拟雨水入渗改变岩土强度的现象。以位移量作为重要指标,先分析河谷下切和雨水浸润对坡体变形的单独影响,再将二者综合分析,并分析二者的作用权重。结果表明,河谷下切和雨水浸润作用在红层滑坡的变形过程中均扮演重要角色,认为坡体变形的根本原因是以红层特殊岩土性质为基础的2次强度衰减过程:河谷下切引起的坡体卸荷松弛(第一次强度衰减)以及临空面的出现是滑坡发生的基础;长期的雨水浸润作用造成岩体强度软化(第二次强度衰减)是滑坡发展的直接原因。把以龙穆尔沟DH6#滑坡为典型代表的高原红层滑坡的变形机制归纳为:原始地貌→河谷下切→坡体卸荷松弛→岩土强度衰减→水的作用→岩土强度进一步衰减→坡体整体滑移。

Taking the Ditch-Moore #DH6 landslide in Xijiu road（S 101） as typical representation, the deformation mechanism of red bed landslide at Qinghai Plateau affected by valley incision and rainfall infiltration was studied by geological analysis and geotechnical model test. In geomechanical model test, slope excavation is used to simulate the valley incision; and the technique of capillary infiltration is used to simulate the rainfall infiltration. Displacement is an important index of the test. The influence of valley incision and rainfall infiltration on slope displacement are analyzed separately; then a comprehensive analysis of two factors is made; and the roles of two weights are analyzed. The results indicate that valley incision and rainfall infiltration play important roles in the deformation of red bed landslide. The root causes of slope deformation are two strength degradation process based on special ground nature of red bed. （1） Unloading relaxation caused by valley incision（the first intensity attenuation） and the invading surface are the basis for the emergence of landslide; （2） Long-term softening of rock mass strength induced by rainwater infiltration（second intensity decay） is the direct cause of landslide development. Therefore, the mechanism of the red bed landslide is summarized as ＂the original landscape→valley incision→ valley slope relaxation→geotechnical strength decay→rainfall infiltration-＇-geotechnical strength decay further→overall slip＂ by comprehensive analysis as the representative to the Ditch-Moore #DH6 landslide.