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Hydrogeologic settings for fractured rocks

Hydrogeologic settings for fractured rocks. Fractured granite Florissant, CO. Sheeting joints in granite Yosemite,CA. Unloading fractures in granite Scottsdale, AZ. granite, Albuquerque, NM. granite batholith, NE WI. Lineaments in granitic terrain (taken from plane).

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Hydrogeologic settings for fractured rocks

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  1. Hydrogeologic settings for fractured rocks

  2. Fractured granite Florissant, CO Sheeting joints in granite Yosemite,CA Unloading fractures in granite Scottsdale, AZ

  3. granite, Albuquerque, NM granite batholith, NE WI Lineaments in granitic terrain (taken from plane)

  4. vertical foliation, eastern US vertical foliation, Black Canyon of Gunnison

  5. metavolcanics, central WI Precambrian quartzite central WI Fractured crystalline rock, Alps

  6. Columnar jointed basalts Eastern, OR Devil’s Causeway Ireland Volcanic mudflow Clarno, OR

  7. Fractured dolomite, Germany Canyonlands, Utah Dipping carbonates, Pyrennes

  8. sandstone, Kansas sandstone, SE WI sandstone, Arches

  9. clayey till, NW WI

  10. Fractures • Fractures — mechanical breaks in rock • fracture is a term used for all types of generic discontinuities • Joints — dilating fractures; formed under tension • Shearing fractures/faults — formed under compression • surfaces move predominantly parallel to each other • Closing fractures/pressure solution surfaces

  11. Fracture Network Geometry

  12. Comparison of aquifer typesGranular Fractured EffectiveMostly primary Mostly secondary Porosity intergranular pores concentration of joints, fractures bedding plane partings Flow Slow, laminar Possibly fast & turbulent Isotropy More isotropic Probably anisotropic Homogeneity More homogeneous Highly heterogeneous Flow Darcy's law Darcy's law usually applies may not apply Head Minimal variation Can be “flashy” Water Chem Minimal variation More variation

  13. Characteristics of Fractured Aquifers • porosity is primarily secondary • hydraulic conductivity distribution is very heterogeneous • ranging over several orders of magnitude • may be bimodal • frequently anisotropic • flow paths rapid flow in fractures, slower paths in matrix blocks • flow rates may be rapid and difficult to predict • recharge ranges from focused (point) to dispersed (diffuse) • storage is primarily from matrix blocks

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