Abstract

The uplift pressures change the stress state of the rock mass foundation in a coupled hydromechanical process and may compromise the dam stability. Consequently, dam safety regulations specify the maximum values of the hydraulic conductivity and uplift pressures that can usually only be fulfilled after the execution of seepage and uplift control measures. The design of waterproofing and drainage systems is still based on an equivalent continuum approach, even though rock mass foundations are discontinuous media. The analysis of the piezometric monitoring data of several Portuguese large concrete dam foundations reveals that uplift pressures are site-specific and may even vary considerably across a given site, which can be critical for the safety assessment. From the data gathered in several dams, a probabilistic model that can be seen as an a priori prediction model for uplift pressures is proposed. Considering the difficulty in classifying the geologic foundation conditions beneath each piezometer in existing dams, it is assumed that the data come from a mixture of two beta distributions, representing foundations with regular and unfavorable geologic conditions. This model is a significant improvement over available approaches and will be instrumental for the assessment of existing dams and the design of new dams.

摘要

在耦合的流体力学过程中，抬升压力会改变岩体基础的应力状态，并可能危及大坝的稳定性。因此，大坝安全法规规定了水力传导率和抬升压力的最大值，通常只有在执行渗漏和抬升控制措施后才能达到。即使岩体基础是不连续介质，防水和排水系统的设计仍然基于等效的连续体方法。对几个葡萄牙大型混凝土坝基础的测压监测数据的分析表明，抬升压力因场地而异，甚至在给定场地之间可能会有很大差异，这对于安全评估至关重要。从几个大坝收集的数据中，一个概率模型可以看作是一个提出了隆起压力的先验预测模型。考虑到对现有大坝中每个测压计下方的地质基础条件进行分类的难度，假设数据来自两个β分布的混合，代表具有规则和不利地质条件的基础。该模型是对现有方法的重大改进，将有助于评估现有大坝和设计新大坝。