2 research outputs found
Structural geology and geophysics as a support to build a hydrogeologic model of granite rock
A method developed for low-permeability fractured media was applied to
understand the hydrogeology of a mine excavated in a granitic pluton. This
method includes (1) identifying the main groundwater-conducting features of
the medium, such as the mine, dykes, and large fractures, (2) implementing
this factors as discrete elements into a three-dimensional numerical model,
and (3) calibrating these factors against hydraulic data
<cite class="cite"/>. A key question is how to identify preferential
flow paths in the first step. Here, we propose a combination of several
techniques. Structural geology, together with borehole sampling, geophysics,
hydrogeochemistry, and local hydraulic tests aided in locating all
structures. Integration of these data yielded a conceptual model of the site.
A preliminary calibration of the model was performed against short-term (<âŻ1 day)
pumping tests, which facilitated the characterization of some of the
fractures. The hydraulic properties were then used for other fractures that,
according to geophysics and structural geology, belonged to the same
families. Model validity was tested by blind prediction of a long-term (4
months) large-scale (1âŻkm) pumping test from the mine, which yielded
excellent agreement with the observations. Model results confirmed the
sparsely fractured nature of the pluton, which has not been subjected to
glacial loadingâunloading cycles and whose waters are of Na-HCO<sub>3</sub> type