Investigation of Load-Displacement Behavior of Helical Pile in Wet and Saturated Sand with FCV Apparatus

Nowadays, given to the scarcity of Oil and Gas resources onshore, and the increasing demand for construction of facilities in coastal areas the use of deep foundations for providing stability for marine infrastructures, such as Oil and Gas Drilling Rigs and Wind turbines, has gained an increasing attraction. Interests in research of helical piles have been arisen due to the advantages of such foundations. Physical modelling is one of the most common method in practice for performance evaluation of deep foundations which provides with the researcher the capability of repeatability. In addition, it is chip and easy-to-execute method compared to the in-situ pile loading tests. Frustum confining vessel (FCV), is one of the most effective tool for physical modeling approach. FCV has a conical shape, which can convert the vertical applied pressure to the base of the vessel, to horizontal stress and to produce a stress distribution similar to the idealized linear stress distribution of soil in situ. Consequently, each base pressure corresponds to a specific embedment depth in real-world. In this study, a new FCV device with an optimized dimensions with the capability of testing model piles in saturated soil samples was constructed. To the best of the author’s knowledge, the newly constructed apparatus is the only FCV with this capability. After performance evaluation of the device, the load-displacement of a helical pile with one and three helices at different relative densities, both in wet and saturated sand, was evaluated. Results indicate that as the relative density increases the interlocking of the sand and helices increases which yields to an increase in the ultimate bearing capacity of pile. On the other hand, the bearing capacity reduces significantly in saturated sands. Also, increasing the number of helices significantly increases the bearing capacity of the helical pile.