Internal erosional behaviour of dispersive clay stabilized with lignosulfonate and reinforced with polypropylene fiber

The problematic dispersive clayey soils that are widely distributed around the world, causing distress to the structures built by or founded on them, require improvement. In this study, a novel procedure involving the lignosulfonate as an environmentally friendly stabilizer and the polypropylene fiber as a reinforcement material were used to improve the erosion resistance and the mechanical strength of a soil with high degree of dispersivity. Double hydrometer tests, pinhole tests, unconfined compressive strength tests, hole erosion tests, scanning electron microscope tests, and X-ray diffraction tests were carried on the dispersive clay in its dispersive state and when modified by the additives, solely and simultaneously. The results showed that the dispersion potential of the soil drastically decreased due to the lignosulfonate stabilization while the mechanical strength was significantly improved due to the polypropylene fiber reinforcement. Although the polypropylene fiber reinforcement alone was incapable of reducing the dispersivity potential down to the acceptable level, the combined treatment by the lignosulfonate and the polypropylene fiber has resulted in an acceptable erosion resistance and a satisfactory mechanical strength. The simultaneous treatment with 2% lignosulfonate and 0.35% polypropylene fiber caused a significant reduction in soil dispersivity, i.e. from 100% to 23%, thus improving the dispersivity category from the highly dispersive to the non-dispersive. The treatment also increased the soil compression strength by 639% after 7 days of curing and by 2541% after 28 days of curing. In terms of erodibility, the qualitative class of the soil upgraded from the very rapid to moderately slow. (C) 2018 Elsevier Ltd. All rights reserved.