Ass. Lect. Mohamed Adel Ahmed Elkasabgy :: Publications:

Helical screw piles can provide immense construction and performance advantages over the conventional concrete and steel piles. To further exploit their potential advantageous performance, there is a need for thorough and systematic characterization of their performance. For applications that involve dynamic loading, it is necessary to qualify and quantify their dynamic performance. This paper presents the first full-scale vertical and horizontal dynamic field testing program executed on a large capacity helical screw pile. The complete test setup and test procedures are described to provide the basis for future dynamic testing performed on screw piles. A series of quadratic type harmonic loading tests was conducted on a 324 mm diameter steel pile installed 9.0 m into a clayey deposit. The pile was provided with two helices each of diameter 610 mm. A Lazan type mechanical oscillator was used to generate frequency sweep loadings from frequencies below to frequencies above the resonant frequency of the pile-soil-cap system at five force intensities for each loading direction. The acceleration at the level of the centre of gravity of the pile cap-oscillator system was recorded. Conventional soil boring and testing methods were adopted to determine the subsurface soil profile and static soil properties. Dynamic soil properties adjacent to the tested pile area were determined using the seismic cone penetration technique. The initial analysis of the testing results reveals basic dynamic characteristics of the pile-soil system and gives some insights into the interface conditions. In addition, the results of the current project can be employed to evaluate the adequacy of the existing theoretical approaches in order to predict the dynamic response of screw piles. The data presented is therefore considered valuable to other researchers and engineers considering the dynamic performance of helical screw piles.