HELICAL SCREW PILES (HSP) CAPACITY FOR AXIAL CYCLIC LOADINGS IN COHESIVE SOILS

The use of helical anchors has gained popularity and has evolved into several innovative applications, including Helical Screw Piles (HSP). A comprehensive research program is being undertaken to explore the use of HSP for the seismic retrofitting of the foundations of existing structures and for implementation of new buildings in seismic areas. The research is motivated by some needs arisen from the recent upgrade of the Canadian seismic code. This paper focuses on the seismic performance of HSP capacity for axial cyclic loadings in cohesive soils. The main objectives of the paper are to evaluate the geotechnical capacity of this foundation system and to understand its cyclic behavior and load transfer mechanism. A filed testing program was conducted involving monotonic and cyclic load testing of three instrumented HSPs in cohesive-frictional soil. The piles performed well in terms of both pile capacity and displacement under cyclic loading. It was found that 15 cyclic loadings on the piles reduced the axial compression capacity of the pile by less than 10%.