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https://hdl.handle.net/2142/69932
Description
Title
Hydraulic Fracturing in Earth Dams (Boreholes)
Author(s)
Boakye, Samuel Yamoah
Issue Date
1984
Department of Study
Civil Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Abstract
The proposed mechanisms of hydraulic fracturing in earth embankment dam cores and boreholes published by various authors have been outlined and compared in this investigation. An experimental study was conducted which reinforces the fact that hydraulic fracturing in boreholes is a tensile phenomenon.
The case histories of embankment dam leakages associated with hydraulic fracturing were examined in this study and it was found that they provide ample evidence of the widening of existing cracks but no conclusive evidence in support of the definition of hydraulic fracturing as initiation of cracks by the reservoir water pressure. From the areas of observed leakages it was concluded that cross-valley arching is more of a contributing factor to the reduction of stresses and the development of cracks than cross-sectional arching.
Plane strain finite element analyses of embankment cross sections were conducted to evaluate the effects of core geometry, core material properties and shell material properties on the principal stresses in the core of embankments. For the material properties investigated, it was shown that conclusions about the effects of embankment material properties on the likelihood of hydraulic fracturing depend on whether such analyses are focused on the minor principal stresses or on the major principal stresses. The relevance and limitations of such analyses in assessing hydraulic fracturing in embankment dam cores are discussed.
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