基于演化过程的互层斜坡深层倾倒稳定性评价

互层倾倒是一类典型的深层倾倒模式,为准确评价其稳定性,开展互层倾倒的工程地质特性及稳定性评价研究。以雅砻江上游发育的深层倾倒体为典型实例,利用基于演化过程的研究方法,在构建倾倒体工程地质模型的基础上,从变形过程和演化阶段上定量评价斜坡整体稳定性。研究表明:互层倾倒是由块体倾覆和板梁弯曲形成的复合倾倒模式,即:硬岩发生块状-弯曲倾倒,而软岩发生弯曲倾倒;空间上,一个发育完备的倾倒体可划分为:滑动区(A区)、强倾倒区(B区)、弱倾倒区(C区)以及原岩区(D区)。基于实测数据提出的斜坡倾倒定量描述体系,可以作为岩体倾倒变形识别和变形程度分级的基本依据;时间上,互层倾倒演化过程主要经历4个演化阶段:卸荷回弹陡倾拉裂面阶段,初始变形阶段,板梁根部折断、剪切面贯通阶段以及破坏阶段,并最终转化为蠕滑-拉裂模式形成滑坡。该滑动面受强变形岩体中倾向坡外结构面控制,而并非沿最大弯折带发育;滑动区(A区)的出现意味着斜坡最终破坏的发生,对应于演化的第三阶段,为斜坡的极限平衡状态,稳定性系数介于1.0~1.05之间。基于演化过程的评价方法,能有效解决互层倾倒稳定性评价问题。

Stability Analysis of Deep-Seated Toppling in Interlayered Rock Slopes Based on Evolution Process

Toppling in interlayered rock slope is a typical mode of deep-seated toppling. This paper analyses quantitatively its stability using an engineering geology method based on evolution process. With the failure mode, constructed by taking deep-seated toppling in the upstream of Yalong River as typical examples, the paper proposes a deformation zone classification to assess the deformation stage and overall stability of toppled slopes. The research shows that toppling in the interlayered rock slope is a compound pattern formed by block overturning and cantilever beam bending, that is block-flexure toppling in hard rocks and flexural toppling in soft rocks, respectively. Spatially, a well-developed toppling is divided into four parts: the sliding, strong toppling, weak toppling and original rock areas, by using the proposed deformation classification system. In time, a toppled slope mainly experiences four evolutionary stages: unloading and rebound, initial deformation, breaking in flexure, and failure as landslide. In addition, the sliding surface is controlled by the cross-joints in strongly deformed rocks, rather than along the maximum bending zone. The occurrence of the sliding zone means that the final failure of the slope occurs, corresponding to the limit equilibrium state which has a stability factor of 1.0 to 1.05. The results demonstrate that the evaluation method based on evolution process can effectively analyse the stability of toppling in the interlayered rock slope.