深切河谷岸坡应力水平分布型式的讨论

Discussion on horizontal distribution pattern of geo-stress in bank-slope of deep valley

驼峰型分布是河谷岸坡地应力水平分布的一种基本形式,但溪洛渡水电站坝区岸坡地应力分布却呈现出不同于驼峰型分布的一种形式,即仅有应力释放区、应力平稳区,而无明显的应力增高区。通过对测试数据及地形地质条件分析认为,这种分布形式是在特定的岸坡结构条件下形成,即岸坡下部或坡脚部位发育有近水平或缓倾坡外的、延伸较长的软弱结构面。对于驼峰型分布,通过对6个工程实例测试数据的统计分析发现,控制应力增高区底界水平深度、最大应力集中程度的主要因素是相对坡高,前者与相对坡高呈正相关,后者与相对坡高呈负相关,进而初步建立了它们之间的经验关系式。针对大型地下厂房布置所涉及的水平深度范围(500~600m以外),提出了岸坡地应力水平分布的三种工程类型:普通驼峰型、单调上升型和上升平稳型。研究所得结论为岸坡地应力分布计算提供参考。

The hump-shaped distribution is a basic pattern of the horizontal distribution of the geo-stress in the bank-slope of valley,however,the geo-stress in the bank-slope within the dam site of Xiluodu Hydropower Station presents a pattern that is different from the hump-shaped distribution,i. e. only stress releasing zone and stationary stress zone exist there without obvious stress-concentrated zone. Through the analysis made on both the measured data and the topographical-geological condition,it is considered that this kind of the distribution pattern is formed under the specific structural condition of the bank-slope. A longerextended weak structural plane that is nearly horizontal or outside of gentle-inclined slope is developed at the lower part or the toe of the bank-slope. For the hump-shaped distribution,it is found out through the statistical analysis on the measured data from 6 projects that the main factor for control the horizontal depth of the bottom boundary of the stress-concentrated zone and the maximum stress concentration degree is the relative slope height,for which the former is positively correlated with the relative slope height and the latter is negatively correlated with the relative slope height,thus the empirical relationship between them is preliminarily established. For the horizontal depth range（ outside of 500 - 600 m） related to the layout of large-scaled underground powerhouse,three engineering patterns of the horizontal distribution of the geo-stress in bank-slope are put forward,i. e. normal hump-shaped,monotone ascending-shaped and stationary ascending-shaped. The conclusion obtained from the study can provide references for the calculation of the geo-stress distribution of bank-slope.