Numerical analysis of geo-filters with reference to an Italian case-history

: Geotextile filters are geosynthetic tubular containers, which are filled by pumping a fluid mixture of water and soil: the permeability of the geosynthetic allows the water to drain so that at the end of the installation a relatively solid nucleus can be obtained. Taking advantage of this feature, geo-tubes have been widely used for the storage of sludge of various types and origins. The paper presents a case-history of an application in Northern Italy, where fine sediment accumulated on the bottom of an artificial basin, Valdaora lake, in Alto Adige (Italy) was removed to ensure the correct functioning of the bottom spillway of the dam. Approximately 2,500 m3 of sediments were stored six geo-tubes, organized in a stacked configuration. At the end of the dewatering process, they were left in situ and used as storage containers, after having covered them with earth, thus becoming an integral part of the slope. Given that there are not closed-form solutions available for the stacked configuration, a numerical analysis was performed by means of the Flac 2D code, in order to evaluate the stress level in the geotextile during the various construction phases and to highlight critical aspects of this composite structure.