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developed in a rock mass. The number of sets of fractures in an area can be
statistically determined by contouring the pole points and in rose diagram.
As weathering will affect surface exposures and their fracture network,
bore hole data will provide complementary information for the interpolation
of fracture network and its attributes at depths. Later, this is compared with
the data obtained from hydraulic tests on bore holes to get an idea about the
hydraulic attributes related to the fracture set volumes. The combination of
all these data helps generating the calculated hydraulic attributes of fracture
networks for numerical modelling of fracture aquifers.
Studies in many crystalline rock terrains world over has shown that highly
transmissive fractures occur locally as clusters in a near-horizontal form
embedded within an extensive network of less transmissive fractures
(Fig. 1).
Figure 1. Vertical cross section and conceptual model of the US Geological
Survey's fractured rock research site near Mirror Lake, New Hampshire.
Four clusters of highly permeable fractures labelled A-D occur in the less
permeable fractured rocks. Borehole packers are closed sections
(after Rutqvist and Stephansson, 2003).
The weathered zone is also an important source of groundwater in hard
rock terrain. In many developing countries in Asia and Africa, large diameter
dug-wells tap water from this zone. The thickness of the weathered zone
depends on the geomorphological, climatic and lithological conditions.
Electrical resistivity and seismic refraction methods are quite helpful in
estimating the thickness of this zone.
GROUNDWATER FLOW
The characterization and prediction of flow and transport through fractured
hard rock mass is extremely difficult as the geometry of the flow and path
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