Dynamic Passive Pressure on Abutments and Pile Caps
This study investigated the lateral load response of a full-scale pile cap with nine different backfill conditions, more specifically being: 1) no backfill present (baseline response), 2) densely compacted clean sand, 3) loosely compacted clean sand, 4) densely compacted fine gravel, 5) loosely compacted fine gravel, 6) densely compacted coarse gravel, 7) loosely compacted coarse gravel, 8) a 3-ft wide densely compacted fine gravel zone with loosely compacted clean sand backfill, and 9) a 6-ft wide densely compacted fine gravel zone with loosely compacted clean sand backfill. The pile cap was loaded using a combination of hydraulic load actuators and an eccentric mass shaker. The actuators were used to slowly push (statically load) the pile cap to incrementally larger target displacement levels. At each displacement level, the actuators were used to cyclically displace the pile cap a small distance, and the shaker was used to apply a dynamic loading on top of the static holding force from the actuators. Hence, the results presented in this report address static, cyclic, and dynamic loadings. The results of this study include horizontal load versus displacement relationships for the pile cap with differing backfill conditions and earth pressure distributions along the pile cap face. The results also include comparisons between measured and theoretically-based or calculated values. Additional results include descriptions of vertical displacement, horizontal displacement and cracking of the backfill. The stiffness and damping for the pile cap with the different backfill conditions were also determined.