L'utilizzo del metodo agli elementi finiti nella trasmissione di fluido interstiziale in terreni piroclastici

Abstract. In this paper we present an application, related to only water transport routines, of the numerical code we have been performing, to a parametric study of water infiltration through a stratified pyroclastic soils affected by rainfalls histogram similar to those measured during April and May 1998 around Sarno areas (Campania, Italy). In order to explore perched water table set up by unsaturated-saturated transition, in particular through light soil layers, some calculations were carried out, considering different lateral water flows intensity. In order to study water transport through a porous material, we performed a monodimensional numerical model by the Finite Elements Method (F.E.M.) to solve the related non linear differential equations (PASCULLI & SCIARRA, 1998a, 1998b). The starting points were: the DARCY law, for the velocity, and a particular form of the scalar balance equation, including the variation of the area through which both heat and water flow into the porous material. Both the area variation capability and distributed water sources and sinks allow to take into account a lateral flow. Furthermore an unsaturated-saturated simple algorithm was performed. Another important characteristic of the model is the feasibility to adopt the more suitable diffusion and permeability coefficients. The model was tested both numerically by the quasi-analytical solution of HAVERKAMP (1977) and experimentally .