Effect of Different Soil Saturation Conditions on The Ultimate Uplift Resistance of Helical Pile Model

Abstract

Helical piles have many properties over the other types of piles systems include high tensile capabilities, the possibility of fast installation, applying load immediately after installation, and suitability for most soil's condition. In addition to that, helical piles have relatively less noise during installation; they represent a cost-effective alternative to conventional pile types. The use of helical piles grows in the world in the last fifty years. Many studies concentrate on the performance of this type of piles in fully saturated and dry soils. The achievement of the helical pile in unsaturated soils is rarely studied. So, to cover this small-scale demand model of the helical pile with double helices has been tested. Twenty tests were performed on three different models (pile with single helix, pile with double helices, and pile with triple helices) and pile shaft only, embedded in different conditions of soil saturation (fully saturated, partially saturated, and dry soils) under uplift loading. Three different matric suction of partial saturation were used of 6.5, 7.4, and 9.6 kPa. The results obtained from the tests showed that the highest value in the unsaturated soil was at suction 6.5 kPa compared to other soil saturation conditions. The results mention that model piles embedded in dry soil have lower values of ultimate uplift capacities. The increment in uplift resistance of additional helices of single double and triple helices than that of shaft pipe embedded within dry soil shows an increment by approximately about 170, 240, and 282% respectively, for fully saturation soil, the increment about 342, 463, and 585% respectively, and by about 400, 429, and 475% respectively for matric suction of 6.5 kPa.

Keywords

• helical piles
• partially saturation
• pile resistance
• uplift bearing capacity
• spacing ratio
• matric suction