Stability assessment methods for huge high-steep unstable rock mass based on damage theory
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摘要: 大型高陡危岩在自重荷载及人类工程活动等多因素共同作用下，其底部区域损伤劣化速度更快，成为影响危岩整体稳定性的“薄弱环节”，易发生底部压裂，引发整体失稳。传统方法将这类大型危岩视作整体，忽略了薄弱区域对危岩整体稳定性的影响，可能导致计算结果与实际情况不符。基于此，文章针对高陡岩体底部压裂失稳模式，引入损伤理论，提出了考虑底部薄弱区域损伤演化的稳定性评价方法。以三峡库区左岸箭穿洞危岩为例，采用规范推荐的倾倒与滑移工况稳定性评价法和本文提出的基于损伤的底部压裂破坏稳定性评价法进行了对比计算，前者算得稳定系数分别为5.49和1.82，后者得到压剪与压张稳定系数分别为1.11和1.06，表明考虑底部薄弱区域岩体损伤的评价方法与实际情况更加相符。研究还发现当高陡危岩高度一定时，底部薄弱区域范围越小（即高占比越大），其受到的上覆荷载越大，当高占比大于10后对上覆荷载的影响明显减弱。当高占比一定时，底部薄弱区域上覆荷载增长率与危岩高度呈线性相关。研究结果可为大型岩质崩塌防灾减灾提供一种新的分析思路与参考。Abstract: Huge high-steep unstable rock mass is more prone to failure of fracturing-crashing at the bottom due to self-difference under the combined action of multiple factors such as dead weight load and human engineering activities. The rate of damage and deterioration of the bottom zone is faster, which becomes the weak link affecting the overall stability of the unstable rock mass.The mechanical difference of such huge rock mass is often neglected in the conventional stability analysis. Based on the damage theory, a method for assessment the stability of high-steep unstable rock mass is proposed, which takes into account the difference of rock mass and damage. The Jianchuandong unstable rockmass was taken as an example, and the comparison between the standard method and the method proposed in this paper shows that the method considering the damage zone is more consistent with the actual situation.Our study also indicates that when the height H of high-steep unstable rock mass is determined, the smaller the weak zone at the bottom (that is, the greater the ratio of H/h), the greater its overlying load is. The influence on overlying load is obviously weakened when the ratio of H/h is more than 10. The growth ratio of overlying load is only related to the ratio of H/h, and it doesn’t change with H. When the ratio of H/h is constant, the growth rate of overlying load of the weak zone at the bottom is linearly correlated with H. This research can provide a new analytical method and reference for geohazard prevention and reduction of huge rock collapses in southwestern mountain areas of China.
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