TY - JOUR
T1 - Influence of fibers on the shear strength and dewatering performance of geotextile tubes
AU - Khachan, M. M.
AU - Bhatia, S. K.
N1 - Funding Information:
This study was supported by the National Science Foundation (NSF) (CMMI 1100131), the Geosynthetic Institute (GSI) and the Wen-Hsiung and Kuan-Ming Li Graduate Fellowship of Syracuse University. The authors would like to thank P. Kaye and V. Ginter of TenCate for providing geotextiles, and BASF Corporation for providing the cationic polyacrylamide flocculant.
Publisher Copyright:
© 2015 Thomas Telford Ltd.
PY - 2016/10/1
Y1 - 2016/10/1
N2 - Geotextile tubes have been widely used for the dewatering of high water content fine sediments. Fine sediments include lake sediments, organic soils and coal combustion products, which generally have low shear strength. Several researchers have emphasized the effect of the retained sediment (filter cake) properties on dewatering performance and stability of the geotextile tubes. Maintaining retained sediment properties, in particular permeability and shear strength, allows for faster dewatering time, better retention of sediments and improved stability of the geotextile tubes during multiple filling stages and during the tube stacking process. Several studies have shown that the use of synthetic fibers can increase the shear strength of sand, silt and clays. However, the use of fibers to improve the strength of retained sediments in geotextile tubes has not been explored. In this study, three synthetic fibers varying in length and diameter were used to evaluate the effect of fibers on the dewatering performance and shear strength of the fine sediments. A cationic polyacrylamide flocculant was used as an optimum conditioner for the selected sediment. The fibers were mixed with the flocculant conditioned slurry at 0.25, 0.5, 1 and 2% fiber concentration by mass of the dry solids. The effect of fibers on the undrained shear strength of the dewatered sediments was evaluated using a lab vane test, fall cone test and undrained unconsolidated triaxial test. Jar tests and pressure filtration tests were also conducted to evaluate the effect of fiber on the required flocculant dosage and on the dewatering performance. Based on the results of this study, 0.5% of F1 fiber type was found to be the optimum fiber concentration, yielding an approximately 100% increase in undrained shear strength. It was also found that the diameter and length of the fibers play a significant role in altering the undrained shear strength of the tested sediments. The relatively short (6 mm) and thick (38 μm) fiber did not yield an increase in shear strength for all the tested fiber concentrations, whereas thin fibers (9 μm) of similar length increased the shear strength by 100%. Furthermore, it was found that the use of fibers at any concentration decreases the required optimum doses of flocculant by about 15%, and increases the dewatering rate of the effluents by about 50%.
AB - Geotextile tubes have been widely used for the dewatering of high water content fine sediments. Fine sediments include lake sediments, organic soils and coal combustion products, which generally have low shear strength. Several researchers have emphasized the effect of the retained sediment (filter cake) properties on dewatering performance and stability of the geotextile tubes. Maintaining retained sediment properties, in particular permeability and shear strength, allows for faster dewatering time, better retention of sediments and improved stability of the geotextile tubes during multiple filling stages and during the tube stacking process. Several studies have shown that the use of synthetic fibers can increase the shear strength of sand, silt and clays. However, the use of fibers to improve the strength of retained sediments in geotextile tubes has not been explored. In this study, three synthetic fibers varying in length and diameter were used to evaluate the effect of fibers on the dewatering performance and shear strength of the fine sediments. A cationic polyacrylamide flocculant was used as an optimum conditioner for the selected sediment. The fibers were mixed with the flocculant conditioned slurry at 0.25, 0.5, 1 and 2% fiber concentration by mass of the dry solids. The effect of fibers on the undrained shear strength of the dewatered sediments was evaluated using a lab vane test, fall cone test and undrained unconsolidated triaxial test. Jar tests and pressure filtration tests were also conducted to evaluate the effect of fiber on the required flocculant dosage and on the dewatering performance. Based on the results of this study, 0.5% of F1 fiber type was found to be the optimum fiber concentration, yielding an approximately 100% increase in undrained shear strength. It was also found that the diameter and length of the fibers play a significant role in altering the undrained shear strength of the tested sediments. The relatively short (6 mm) and thick (38 μm) fiber did not yield an increase in shear strength for all the tested fiber concentrations, whereas thin fibers (9 μm) of similar length increased the shear strength by 100%. Furthermore, it was found that the use of fibers at any concentration decreases the required optimum doses of flocculant by about 15%, and increases the dewatering rate of the effluents by about 50%.
KW - Dewatering
KW - Geosynthetics
KW - Geotextile tube
KW - Shear strength
KW - Synthetic fibers
UR - http://www.scopus.com/inward/record.url?scp=84988649507&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84988649507&partnerID=8YFLogxK
U2 - 10.1680/jgein.15.00053
DO - 10.1680/jgein.15.00053
M3 - Article
AN - SCOPUS:84988649507
SN - 1072-6349
VL - 23
SP - 317
EP - 330
JO - Geosynthetics International
JF - Geosynthetics International
IS - 5
ER -