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Abstract
The first section of this thesis (Chapter 2) describes the creation and analysis of a database on concrete and masonry dam incidents known as CONGDATA. The aim was to carry out as complete a study of concrete and masonry dam incidents as was practicable, with a greater emphasis than in other studies on the geology, mode of failure, and the warning signs that were observed. This analysis was used to develop a method of very approximately assessing probabilities of failure. This can be used in initial risk assessments of large concrete and masonry dams along with analysis of stability for various annual exceedance probability floods.
The second and main section of this thesis (Chapters 3-6) had its origins in the results of Chapter 2 and the general interests of the author. It was found that failure through the foundation was common in the list of dams analysed and that information on how to assess the strength of the foundations of dams on rock masses was limited. This section applies to all applications of rock mass strength such as the stability of rock slopes.
Methods used for assessing the shear strength of jointed rock masses are based on empirical criteria. As a general rule such criteria are based on laboratory scale specimens with very little, and often no, field validation.
The Hoek-Brown empirical rock mass failure criterion was developed in 1980 for hard rock masses. Since its development it has become virtually universally accepted and is now used for all types of rock masses and in all stress regimes. This thesis uses case studies and databases of intact rock and rockfill triaxial tests collated by the author to review the current Hoek-Brown criterion. The results highlight the inability of the criterion to fit all types of intact rock and poor quality rock masses. This arose predominately due to the exponent a being restrained to approximately 0.5 to 0.62 and using rock type as a predictor of mi. Modifications to the equations for determining the Hoek-Brown parameters are provided that overcome these problems.
In the course of reviewing the Hoek-Brown criterion new equations were derived for estimating the shear strength of intact rock and rockfill. Empirical slope design curves have also been developed for use as a preliminary tool for slope design.