UBC Theses and Dissertations
Estimation of compressive load bearing capacity of helical piles using torque method and induced settlements Khan, Muhammad Umair Shabbir
Helical piles are deep foundations that have a helix at the end. The traditional approaches to determine the load capacity such as loading tests and in situ tests (i.e. SPT, CPT and LCPC) are not economically feasible for the small scaled constructions, for which helical piles are generally recommended. In order to estimate the ultimate load that helical piles can carry, torque method is thus mostly used. Torque method does not account for the possible settlements induced at calculated loads. Settlement induced is the main load capacity governing factor for deep foundations, as they are considered failed when a settlement more than the permissible amount is attained. The possibility that the piles might fail well before the calculated load is achieved because of excessive settlements make the results of torque method dubious. This research attempts to investigate the torque method for the settlements and for its precision. For this purpose, seven RS2875.203 helical piles were installed and their ultimate compressive loads are calculated using the torque method. On seventh pile, static axial compression test was conducted. The settlements at torque method’s ultimate loads are determined from the load movement curve of compression test. Results underscore that the settlements at torque method’s ultimate and allowable loads are within the permissible amount. The load movement curve of compression test is interpreted using different failure criteria to calculate the failure load. Results show that 10% failure criterion is the most suitable criterion to interpret the load movement curve of RS2875.203 helical piles. Additionally, different bearing equations are used to compute the ultimate compressive loads of helical piles. Result suggest that the loads calculated using torque method and bearing equations correlate well with each other.
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