Soil plugging behaviors and CPT based installation resistance analysis of open-ended helical pile embedded in clay

The soil plugging effect generated during the installation of open-ended helical piles affects their constructability and bearing capacity. This study conducted the soil plugging behaviors field tests of open-ended helical piles installed in clay, and the installation resistances were further analyzed based on CPT. The factors influencing soil plug development were thoroughly examined, and the soil plugging performance of helical piles was compared with jacked and driven piles. The results indicate that the incremental torque ratios (ITR) remains constant, while the incremental filling ratios (IFR) and plug length ratios (PLR) initially rapid decrease and then stabilize at approximately 40%. Both IFR and PLR exhibit logarithmic relationships with the reciprocal of ITR. The torque and plug resistance histories can be predicted by CPT. The unit plug resistance remains nearly constant regardless of inclination angles. The effect of inner diameter differs from that of previous studies, as the length and inner diameter of the tested piles varied simultaneously. The PLR of helical piles is greater than that of jacked piles when the IFR is below 50%, and less than that of driven piles when the IFR exceeds 50%, which is further validated by the calculated plug resistance of various pile types.