Influence of Synthetic and Natural Fibers on Dewatering Rate and Shear Strength of Slurries in Geotextile Tube Applications

This study investigates the effect of fibers on the dewatering time, filter cake properties, and shear strength of filter cakes with fine-grained silty clay. Synthetic nylon fibers with lengths of 6, 12, and 18 mm and one natural jute fiber with an average length of 8 mm were added to slurries with 33 % fines in concentrations of 0.5 % by soil mass. Optimum dose tests for particle flocculation showed that slurries reached a turbidity of 20 NTU with up to 19 % less flocculatant material compared to slurries with no fibers. Pressure filtration tests showed that the dewatering time decreased significantly with both synthetic and jute fibers, but were not dependent on fiber length. However, fall cone tests and unconsolidated undrained tests showed that the increase in shear strength was dependent on fiber length. Increases in shear strength were over 100 % with 12 mm nylon fibers, while filter cakes with 6 and 18 mm nylon fibers increased the shear strength by 43 %. Jute fibers did not show as high of a strength gain as the nylon fibers, but did increase dewatering times by an average of 14–22 % compared to filter cakes with nylon fibers.