Abstract:

There are several numerical modelling approaches of speleogenesis in existence today. They take into account physical and chemical laws for flow and dissolution in fractured carbonate aquifers. Nevertheless, the initial void networks considered by these models generally do not correspond to the fracturing reality. The approach proposed here aims to simulate speleogenesis in an aquifer characterized by a fracture network, while matching field reality as closely as possible and respecting geometrical properties. Using statistical and geometrical parameters obtained by field observations and analogue experiments, it is possible to generate 3-D realistic networks in terms of the relative position of joints that control the overall network connectivity. Once the fracture networks are generated, they are adapted and incorporated in a 3-D ground water flow and transport finite element model. The flow simulations in the fracture networks allow determination of the spatial distribution of flow velocities for the initial configuration. This distribution, added to other information such as age and travel time, is used to simulate the evolution of the apertures of the different elements. This paper mainly presents the theoretical basis for the proposed method, from the fracturing model to the incorporation of the generated network in the flow model. Then, it describes the principles leading to forthcoming first benchmark simulations which will be used to develop the analogical rules concerning karst aquifer evolution, and for lead sensibility analysis.