Stability Analysis of Jointed Rock Mass Foundation of Concrete Gravity Dam and Slope Stability of Abutment
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Date
2023-12
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Addis Ababa University
Abstract
For high-performance operations and the safety of the dam structures, it is essential to study the rock mass foundation of major dams. Numerical modeling can be used to overcome some of the limitations associated with researching rock mechanics, such as the need for extensive laboratory testing for geotechnical engineering of dam foundations. Numerous researches have employed numerical modeling analysis to identify the failure model and resolve foundational issues pertaining to rock mechanics. The aim of this study is to examine and analyze the stability of the jointed rock mass foundation and abutment slope stability of Koysha RCC dam. The foundation of the concrete dam is affected by complex geology, and two sub-vertical joint sets and one sub-horizontal joint set are
dipping sub-parallel to the river direction, frequently infilled with thick, soft compressible clay and decomposed rock remnants. The joints are cutting each other. In this research, a distinct element model (DEM) tool, namely 3DEC 5.20, is used to study and analyze the stability of the foundation. This model enables the building of material and joint models as discontinuous mediums.
Secondary sources have been the main sources of the required material properties. The Mohr Coloumb elastic, completely plastic model served as a representation of the constitutive block model of the rock and soil components. Perfectly elastic joint model properties served as a representation of the joint
qualities. In addition to the discontinuum medium, the equivalent continuum concept was used to reduce calculation times and simplify the study.
The results of the central foundation analysis indicated that the jointed rock foundation of the dam was in a state of significant deformation along the infilled J2 joint under all loading conditions. The displacement keeps propagating laterally and vertically following the infill materials along the joint.
The result of the abutment analysis revealed displacement of left crest foundation of the dam. From the compressional z-displacement and the pattern of the displacement along the infilled J2 joint set, the research concluded that the infilled material may be responsible for the deformation rather than the joint itself. Generally, the dam body and the whole rock mass foundation of the dam are found to be stable, except for zones of weakly infilled materials along the J2 joint. In order to improve these weak zones along the joint, remedial measures have recommended based on the results of the analysis carried out for improvement by cement grout.
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Keywords
Stability Analysis, Infilled Joint, Deformation, Foundation Improvement.