Retaining of dredging waste using geotextile tubes: analysis of the dewatering and undrained shear resistance of the sludge cake

The city of Rio Grande has its economy linked to coastal and port activities and has a port complex of high economic importance for the region. To maintain the depth of the port channels, periodic dredging operations are carried out, as occurred in the Port of Rio Grande between 2018 and 2020. Approximately 16 million m³ of sediments were removed from the channel and deposited in disposal zones. There has been an attempt to develop techniques that carry out the reuse and disposal of dredging waste more appropriately, seeking to minimize environmental impacts by avoiding inappropriate open-sea or onshore disposal. Within this context, this work aims to evaluate the potential of the retaining and dewatering process of dredging waste in geotextile tubs (linear geoforms, geobags e etc). This technique reduces the volume of dredged mud through desiccation and allows the geotextile tubs to be installed in sedimentation basins onshore or coastal protection structures. Thus, the present study evaluated the dewatering and filtration efficiency of these systems through tests of small bags. The advantages of adding flocculation polymer and the behavior of undrained shear strength over time of the retained cake were evaluated.