Suitability of jetted and grouted precast pile for supporting mast arm structures

Abstract

Jetted and grouted precast piles (JGPPs) are prefabricated piles installed utilizing jetting and pressure grouting. These piles are well-suited for urban environments as they overcome the inherent drawbacks of currently chosen deep foundations (e.g., noise and vibration disturbances due to pile driving, quality control issue with cast-in-place construction). Past studies in a large test chamber facility have shown that JGPPs can support very high axial and torsional loads owing to their improved skin and tip resistances subsequent to the side- and tip-grouting. However, this new pile has not yet been implemented in practice due to the lack of field verification of its constructability as well as load resistance. This paper presents the full-scale field construction of two JGPPs and the load test program performed to investigate the applicability of the new pile as a foundation for miscellaneous structures. As such structures are subjected to high torsion and lateral load during severe wind-loading (e.g., hurricanes), the test program included combined torsion and lateral loading as well as simple lateral loading. An actual pole – mast arm assembly was used in the coupled torsion and lateral load test to simulate the typical field-loading scenario. The load was applied using a crane and the pile’s rotations and translations were monitored using the novel instrumentation systems. The field tests showed that JGPPs possess high torsion and lateral resistances compared to identically sized drilled shafts, which is a common foundation type used for such structures. The two methods available for predicting axial resistance of the new pile are found to be suitable for the estimation of torsional resistance as well. It was also found that the concurrent application of torsion significantly reduces lateral resistance of the new pile foundation as observed for drilled shafts. In general, the study reveals that the JGPPs are well-suited foundations for miscellaneous structures.