Optimization of grouting method and axial performance of pressure-grouted helical piles

Pressure-grouted helical pile (PGHP) is an innovative piling system that allows a significant increase in helical pile capacity with relatively low additional cost. The pile is constructed by applying pressurized grout during the installation of conventional helical piles. The grout is injected into the ground through two nozzles welded to the hollow pile shaft. This paper presents a comprehensive laboratory study to investigate the effect of three different nozzle configurations on the shape and axial performance of PGHP. The results reveal a significant increase in the PGHP shaft resistance over that of the un-grouted helical pile due to the formation of a continuous grout column with a larger diameter, higher friction angle at the pile–soil interface, and higher lateral earth pressure around the pile. The shape and diameter of the grout column created depend on the nozzle configuration used for grout injection. An increase in the end-bearing resistance is observed due to grout dissipation into the supporting soil voids. The study also shows that PGHPs installed with the third nozzle configuration have the fastest installation rate and the highest compression and pullout resistances. Thus, the third nozzle configuration is recommended for PGHP construction.