考虑极限倾覆失效的混凝土坝整体稳定状况分析

Analysis on Global Stability Condition of Concrete Dams in Consideration of Limit Overturning Failure

主要失效模式的识别和确定是大坝安全分析中的重要内容,传统分析将正常使用极限状态和极限失效状态混合考虑。针对这一问题,以重力坝为例,将应力超限失效包含在极限倾覆失效状态中,由力矩平衡推导得到了极限倾覆失效的状态函数;同时,提出了相应状态函数中参数的确定方法和估算方法。以此为基础,建立了包含主要极限稳定失效状态的重力坝的通用系统失效模型。分析了某在役重力坝的整体稳定状况,结果表明对于坝基为软弱完整基岩的情形,应考虑基岩强度不足引起的重力坝-基岩系统极限倾覆整体失效模式。

Identification and determination of main failure modes are important in dam safety analysis. In traditional analysis, serviceability limit states （e. g. , overstressing） are considered together with ultimate limit states. Over- stressing may be the cause and initiating factor leading to global failure and must be analyzed. However, overstress- ing in itself is, generally, not a global limit failure mode. In this paper, this bearing capacity failure mode is in- cluded in the limit overturning failure mode. With gravity dam as an example, the limit state function for overtur- ning is derived with the help of moment balance relationship ; and methods of determining and estimating the param- eters in the function are also discussed. On this basis, a general system failure model for gravity dams in considera- tion of main ultimate limit states is proposed. An in-service gravity dam is investigated, and the results show that, for gravity dams on intact weak rock foundation, the limit state for overturning caused by overstressing must be taken into account due to inadequate rock crushing resistance.