Étude sur modèles physiques du mécanisme de la pollution des eaux souterraines par liquides miscibles (Saumures) et non miscibles (Hydrocarbures)

¹ Chargé de Recherches au C.N.R.S Institut de Mécanique des Fluides de l'Université Louis-Pasteur, Strasbourg
² Institut de Recherches au C.N.R.S Institut de Mécanique des Fluides de l'Université Louis-Pasteur, Strasbourg

Résumé

General subject of research. The researeh described covered problems associated with the danger of the Alsace plain aquifer becoming polluted by bath accidental leakage of petroleum products and brine seepage from storage areas. Physical models allow the effect of the main characteristic parameters of possible ground water pollution development to be determined ; by simplifying the natural medium whilst preserving its elementary structure, a direct picture of the flow pattern is obtained. Development of the mixing zone associated with brine seepage into an aquifer. The mixing zone starts out from a brine source in a uniform flow of water. Tests on a two-dimensional model showed the three following types of flow : a) Downward flow, i.e. vertical infiltration. b) Entrainment flow, i.e. the spread of the mixing zone along the direction of water flow. c) Unstable flow, i.e. an intermediate stage between (a) and (b). By means of a theoretical scheme, the entrainment effect was related to the general problem of spread in a porous medium. The data obtained were found to agree satisfactorily with the results of concentration measurements in the mixing zone. Similarity criteria are required to extend and generalise the quantitative data. Transposition of the various flow types is feasible on a physical model : extrapolated full-scale data require comparing with in-situ test data. Laboratory tests on accidental aquiler pollution by petroleum products. The basic investigation in the research programme on the effects of leakage from a petroleum pipeline showed the two aspects of the spread of petroleum in the aquifer, i.e. the fixing of the crude oil and the entrainment of soluble particles in the aquifer. The applied research carried out to determine means of protecting the alluvial aquifer against leakage from pipelines passing underneath rivers was followed by tests on a hydrodynamic anti-pollution device. Research is now in progress on water and ground pollution by refinery product conveyors. The first tests are investigating the transfer effects taking place at the initial contact surface between the stationary petroleum product and the aquifer flow.