Author(s): Mayerle Giampietro; Brotto Maria Teresa; Passacantando Giancarlo; Cazzuffi Daniele; Ferraiolo Francesco; Vicari Marco
Linked Author(s):
Keywords: Filter mattress; Seabed protection; Hydraulic properties; Laboratory tests
Abstract: In order to assure the complete defence of the Venice lagoon from high waters, including exceptional occurrences, the solution based upon the temporary closure of all the three Venice lagoon inlets through a line of mobile flood barriers, has eventually emerged as the only solution able to fully respond to the required objectives. Similarly to other interventions carried out in the world to regulate tidal floods (Thames, Scheldt), the selected solution for the seabed protection involves a prefabricated mattress, assembled in a plant, wound onto a floating cylinder and transported to the site where it is laid on the seabed by means of a special pontoon. The 40 mm thick ballasted filtering mattress (BFM) consists of three basic elements: a lower filtering polypropylene, nonwoven geotextile; a polypropylene geomat, reinforced with double twist steel wire mesh, to entrap the ballasting gravel; an upper polypropylene, nonwoven geotextile to contain the material; the total structure is interconnected by steel crews. In order to verify the hydraulic characteristics of the filtering mattress, a series of laboratory and in-situ tests has been carried out both on the single components and the whole mattress, covering the following aspects: hydraulic properties before and after different energy impact tests carried out on 2 soil types (silt and sand); tensile properties (MD, XD) before and after different energy impact tests; lifting tests on assembled units to verify the resistance of both longitudinal and transversal joints. The paper presents the required characteristics, the test methodology and results which have allowed to select the materials to be eventually adopted for the installation.
Year: 2007