Experimental study on horizontal bearing behaviors of different types of full-scale piles under reciprocating horizontal loads

The field pseudo-static tests on 38 prototype piles in in-situ soil conditions, which contain prestressed pipe piles, prestressed squared piles and bored cast-in-situ piles, are made in a typical soft soil site of Hangu, Tianjin. The bearing and seismic behaviors of all kinds of full-scale piles under the pile-soil interaction subjected to low-cycle reciprocating horizontal loads at the pile top are studied. The failure modes, load-displacement relationships and displacement ductility among the prestressed pipe piles, composite-reinforced piles with distributed non-prestressed reinforcements and bored cast-in-situ piles are compared. The results indicate that the regular prestressed pipe pile has poor ductility and is brittle during failure. The displacement ductility and energy dissipation capacity of the composite-reinforced piles are obviously improved by adding non-prestressed reinforcements in addition to prestressed steel bars. This consequently leads to the ductile failure mode. Therefore, adding conventional steel without prestress is an effective measure to improve the seismic performance of prestressed piles. The displacement ductility factor of all the bored cast-in-situ piles with different reinforcement ratios exceeds 4.5, which means that their ductility and energy dissipation capacity are good. The displacement ductility factors of both the composite-reinforced piles and bored cast-in-situ piles increase at first then decrease with the reinforcement ratio of the increasing non-prestressed reinforcements while there is an optimal reinforcement ratio of the displacement ductility.