Back to the first large rockfill dam with an upstream Geomembrane Sealing System (Ospedale,1979)

摘要

Geomembranes have been successfully used to provide a watertight facing on dam for more than five decades. For this Geomembrane Sealing System (GSS), the most frequently adopted solution is an upstream system, because there is no pore water pressure or seepage pressure in the entire dam body. The present paper is dedicated to the oldest large rockfill dam (more than 20 m high) worldwide with this kind of watertightness concept. The geomembrane is a prefabricated bituminous geomembrane of composite structure. In a first part, a detailed description of the concept of GSS is presented.In a second part, the main features of the Ospedale dam (Matrale di U Spidale) are displayed. The important matter discussed is the cover protection of the geomembrane, since the system of small concrete blocks used in Ospedale could be improved. In a third part, the long-term behaviour of the dam along four decades is presented. A steady flow rate related to the seepage through the liner is observed. This percolation level can be considered as very satisfactory, comparing with other monitored dams with an upstream Geomembrane Sealing System.