72 A new concept of karst development based on hydrogeology and geophysics Cooper-Jacob equation (Delay et al., 2004). Bernard et al. (2008) demonstrated that permeability tends to homogenize rapidly over distances of 100–200 m, despite the drawdown data exhibiting significant variability and fractal characteristics. However, this fractal approach applied to fractures does not allow for calibration of the third family of curves. A different modelling approach has recently been applied to interpret pumping tests at the Civaux Nuclear Power Plant 1, located approximately 22 km southeast of Poitiers (see location on Fig. 3). This approach aims to account not only for fractures, but also for the influence of the porosity and permeability of the limestone blocks separating the horizontal discontinuities. The aquifer is conceptualized as containing regularly spaced horizontal discontinuities, which delimit rectangular limestone blocks of uniform thickness b (Fig. 11). For such an aquifer system, Streltsova (1976) proposed two drawdown equations: one for flow through fractures and another for flow through a porous matrix toward a pumping well operating at a constant discharge rate Q. The discontinuities are characterized by a hydraulic conductivity Kf and specific storage Ssf, while the matrix possesses a hydraulic conductivity Km and specific storage Ssm. To incorporate the flow dimensionality of Delay et al. (2004), the general Radial Flow equation of Barker was employed (Barker, 1988). This model generalized radial flow in an unsteady, n-dimensional, dual-porosity fractured aquifer. The flow dimension n governs the transition in flow behavior from linear to radial flow regimes. Exchange between the matrix and the fractures is controlled by a skin factor defined as Sf K b Kb m s s = ( ) / , where bs and Ks denote respectively the thickness and hydraulic conductivity of the skin (the wall zone of the limestone block). Figure 11 illustrates pumping in a confined dual-porosity aquifer. The observed 1. © EDF 2024: these data are the property of EDF; any use is subject to EDF’s prior agreement. Figure 11 Diagram illustrating cylindrical flow system (n=2) in a double porosity aquifer.
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