Abstract

Bangoy et al. [1992] presented a new method aiming at the characterization of a fractured media by pumping tests using at least two observation wells. This method, based on the late-time asymptotic form of the general radial flow model (GRF) given by Barker [1988] allows the determination of the hydraulic diffusivity and the average transmissivity of fractured media. It also allows to outline the fractal groundwater flow in a fractured media and, second, delimits areas of higher hydraulic conductivities. This paper introduces an improved approach which is adapted to pumping tests with only one observation well, i.e. the pumping well. Moreover, this improved approach provides more accurate determination of the fractured transmissivity around the tested well and allows its mapping as a function of the distance (r) from the tested well. The spatial distribution of the fractured transmissivity is then related to either the hydraulic conductivity variation or to the structural features (b) of fractures or structural network. From a standard pumping test, applying this improved approach gives, of course, the aquifer parametres, as well as the delimitation of the areas of higher hydraulic conductivity related to the geometrical features of the fractured network, that can allow to delimit the zone influenced by the fractured well pumping tests, namely the capture zone. This new approach is applied in a case study in fractured network imbedded in a granitic intrusion within the French Pyrenees (Granites of Millas). The fractured transmissivities obtained here increase with the distance from the pumping well.

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