Helical piles with cement injection in medium dense sand

Helical piles are frequently used as foundations of transmission line towers and other structures subjected to both compressive and tensile loads. However, the service performance of these structures can be affected by the uplift response of this type of pile due to the soil disturbance caused by the installation procedure. Two different procedures of cement injection were successfully used to repair this soil disturbance and improve the uplift response of helical piles in soils with some cohesion in a previous study, however these techniques have not been evaluated in cohesionless soils. Therefore, the current study examined the use of two cement injection procedures to improve the tensile and compressive responses of helical piles in medium dense fine sand. For this evaluation, pile loading tests were performed on six identical three-helix piles. The results show that the improvement caused by the cement injection is more significant for the pile uplift performance, although it slightly improves the pile compressive behaviour. The gain in allowable tensile load varied from 40% to 57% according to the injection technique. These preliminary results also indicate that the use of cement injection can provide similar load-displacement response for helical piles under tension and compression.