Mitigation of Expansive Soil Problems by Using Helical Piles with Additives

Abstract

In this study, nine essential additives in addition to three mixed additives with different ratios have been chosen and implemented during the installation of helical pile. The choice took into consideration that some of the additives were cheap and available in the local market; others were waste materials such as ceramic, brick fragments and coal fly ash. Some relatively expensive additives such as silica fumes were also added because it reduces the swelling soil. Three different ratios of each additive were considered according to their types. The ratios are between 0.5 and 6%. The helical piles with double helix (dh=20 mm) were embedded in expansive soil with length 15 cm (L/D=27). From this study, it is found that the 3% silica fumes, 3% coal fly ash, and 6% hydrated lime exhibits good significant improvement which exceeds 50% in reducing uplift movement of helical piles when added during the driven process in expansive soil. Also, 3% mixture of silica fumes to coal fly ash (3:1), 2% of hydrated lime:cement (1:1) shows good degree of improvement which exceeded 50% in reducing uplift movement of helical piles when added during the driven process in expansive soil. Additives such as cement, dust of cement, crushed brick and ceramic, fumed silica and clinker with percent’s not exceeding 6% gave low degree of improvement in reducing uplift movement of helical piles when added during driven in expansive soil.
Keywords: Helical pile, expansive soil, additives, uplift movement, clay soil