Hydraulic Fracturing in Earth Dams (Boreholes)

358 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.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.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD