特高坝及其梯级水库群设计安全标准研究Ⅱ:高土石坝坝坡稳定安全系数标准

我国现行土石坝规范规定1级土石坝坝坡抗滑稳定安全系数为1.5,相应的目标可靠指标为4.2,但同时明确这一标准仅适用于低于200 m的土石坝。本文提出"相对安全率"的概念,把可靠指标和安全系数置于同一平台进行安全水平的关联比较。通过对已建和规划建设高度大于200 m的实际工程进行分析论证,结果表明,对于正常工况,本系列论文第Ⅰ部分建议的200~250 m高土石坝坝坡目标可靠指标取4.45,250 m以上的高土石坝取4.7,可以和坝坡抗滑稳定最小安全系数为1.6和1.7处于同一风险控制标准。这一研究成果可作为规范修订的参考和依据。

Evaluations on the safety design standards for dams with extra height or cascade impacts. Part II:Slope stability of embankment dams

The existing Chinese embankment dam design code specifies an allowable factor of safety of 1.5 in slope stability evaluations, which can be compared to the reliability index of 4.2, also specified by the dam design code. However, the code emphasizes that this criterion is only applicable to dams with heights less than 200 m. Using the theory of "ratio of safety margin" proposed by the authors, and applying case studies for a number of dams higher than 200 m currently being constructed or planned in China, it has been found that the new criteria of factors of safety can be 1.7 and 1.6 for dams with heights of over 250 m and 200-250 m respectively. They are at the same level of safety control to 4.7 and 4.45,their respective allowable reliability indices as proposed in Part I. This finding may be useful in code revision works.