斜坡倾倒变形的工程地质分析

THE IMPLICATION AND EVALUATION OF TOPPLING FAILURE IN ENGINEERING GEOLOGY PRACTICE

近10年来,在山区,尤其是西部山区的工程建设和灾害防治实践中,我们发现越来越多的以"倾倒"为特征的岩质边坡变形破坏和稳定性问题,其出现的频度和造成的危害大有比肩"滑动"破坏这一边坡失稳的传统主题,成为困扰地质工程师和岩石力学工作者的又一难题。这类问题之所以难,是因为建立在以"滑动"为基础的传统边坡稳定性分析方法不再适用这类边坡。本文在大量工程实例的基础上,分析了边坡倾倒变形和破坏的基本特征,从"倾倒"变形破坏的地质过程和变形稳定性分析的基本理念出发,建立了描述倾倒边坡不同变形程度的工程地质模型,这个模型将倾倒边坡分为倾倒-坠覆、倾倒-错动、倾倒-张裂、倾倒-松弛4个区,分别对应不同的变形程度和稳定性状况,提出了各个区的具体特征和定性指标与量化指标相结合的描述指标体系,从而将倾倒的地质显现、力学机理和变形稳定性有机统一,实现了对倾倒边坡稳定性的工程地质评价。与传统的"滑动"问题不同的是,本文没有强调对这类问题采用强度稳定性的评价思路,而建议采用变形稳定性评价的理念,这似乎更适合倾倒变形这类问题的分析和评价。

An increase in the number of rock slope instability case that was characterized with ＂toppling ＂movement was found in the practice of engineering geology in west China in the past decade. The significance of the potential threats caused by toppling failure has arguably moved abreast of that induced by the conventional slope movement type commonly known as ＂sliding ＂,and thus it has become a more pronounced challenge faced by engineering geologists and geotechnical engineers. The critical issue in the study of toppling failure is that the current analytical and/or empirical models are primarily based on the hypothetical slide of rock slopes without considering other forms of movement. The paper analyzes the deformation and failure process of toppling movement in light of the field data obtained from a large number of engineering projects. The study of toppling movement presented here constructed engineering geology models to depict the deformation at various stages and divided the movement into the types of toppling-falling,toppling-slipping,toppling-cracking,and toppling-loosening,which provides systematic qualitative descriptions and quantitative thresholds for the characteristics of each movement type.The study aims at unifying the understanding of geological significance,static and dynamic mechanics,and slope stability analysis to provide means of evaluating the stability of rock slopes prone to toppling failure. The slope stability evaluating criteria are primarily based on deformation process compare to the previous criteria utilizing strength to assess the stability of slope subject to sliding movement.