Pull-out capacity of double-helix screw pile in organic soil

The organic soil used in this study was obtained from Sakarya region, Turkey. According to the system of classification (USCS), the present soil is classified as an organic silt soil with high plasticity (OH). Standard and modified compaction, sieve analysis, specific gravity and organic content tests were done to obtain the engineering properties of organic soil. An experimental investigations on single helical piles were conducted in organic soil. In this work, the effect of spacing ratio of double-helix pile and soil density on the pile performance under vertical pull-out static load were investigated. Double-helix piles were installed and loaded axially in two soil densities: soft and stiff organic soil. Up lift performance was predicted using the axial load versus displacement readings. The pull-out load was applied vertically with the axis of the pile. Test results showed that the ultimate pull-out load capacities of double-helix pile are controlled by the spacing of helical plates. An increase in spacing ratios causing a decrease in ultimate pull-out capacity of helical pile in organic soil. Also, increasing the soil density increasing the ultimate pull-out load capacity. The study showed that the capacity of double-helix pile is greater when the spacing ratios 1 and 2 than 3 and 4. In general, the capacity of double-helix piles with a spacing ratios of 1 and 2 is ranged from 1.25 to 1.77 times the capacity of double-helix pile with spacing ratios of 3 and 4 in both stiff and soft soil respectively. Keywords: Organic soil, helical pile, pull-out, soil classification, pile installation.