Helical Screw Piles Performance - A Versatile Efficient Seismic Foundation Systems Alternative for Structures Rehabilitation, New Sustainable Structures Construction and Infrastructure Delivery

Abstract

Helical screw anchors have been utilized in uplift forces applications for many years and they have gained popularity for bearing load, seismic performance and dynamic applications and evolved into Helical Screw Piles (HSPs). The speed and ease of their installation, as well as the low cost for new construction and repair, make them versatile for many rehabilitation or new construction applications and as an efficient alternative for deep foundations in infrastructure projects when it is suitable. The main objectives of this paper are to explore the available helical piles systems as well the performance of the helical pile foundation systems under monotonic and cyclic axial and lateral loads. In addition, to explore the new helical screw pile systems suitable for seismic retrofitting of existing foundations and for new structures construction; and to explore their design methodology. Among the helical piles configurations available the circular steel shaft helical piles and the square steel shaft helical piles. Among the different systems the fiber reinforced polymer grouted helical screw piles (FRP-G-HSP); and the reinforced grouted helical screw piles (RG-HSP) in which steel fibers were added to the grout. The research methodology involved conducting more than one hundred full scale field load tests on different instrumented helical piles configurations installed in layered soils profiles. The piles included plain helical screw piles (P-HSP); grouted helical screw piles (G-HSPs); FRP-G-HSPs; and RG-HSPs. The axial and the lateral monotonic and cyclic load tests will be presented as well the piles stiffness and the load transfer mechanisms together with the design theories criteria. The results of 3-D Plaxis finite element modeling were used to establish the load transfer mechanism and to validate the design methodology for the considered piles. Case studies for their applications will be presented.