Estudo das características de permeabilidade dos maciços aluvionares

Abstract

This work is concerned with the evaluation of the characteristics of permeabity of aluvionar aquifers conected to rivers. The analysis of transient flow due to periodic fluctuations of a river, the main objective of this work, is used to evaluate the permeability of an aquifer at the river's bank, with aid of simple piezometric observations. The differencial equation governing this type of transient flow was developed by Jacob, who assumed an semi infinite aquifer, completely saturated and confined by an extensive aquiclude. ln this work, Jacob's equation is extended to the case of unconfined aquifers, when the range of water table fluctuation is small. Depending on the initial and boundary conditions, different solutions may be obtained through Jacob's equation. ln this work the solutions proposed by Ferris; Cooper and Rorabaugh; Pinder, Cooper and Bredehoeft; and Marino are presented. A Brazilian aluvionar soil deposit was studied and observations of the river and aquifer's levels were made. The coefficient of permeability of the deposit was then estimated using the procedures proposed by Ferris and Pinder et al, aiming at determination of the coefficient of permeability k based on observations of the aquifer's level and river fluctuations. Both methods were compared using compatible initial and boundary conditions. It is suggested that the procedures, for determination of hydrogeological characteristics of aluvionar soils, as presented in this work, be incorporated to the conventional in situ techniques used in civil engineering.