Behavior of ACIP Piles Socketed in Clay-Shale

Increasing use of ACIP piles, as an alternative to drilled shafts, to support load-bearing structures has resulted in socketing the piles in rocks. In this study, the behavior of eight ACIP piles socketed in soft clay-shale was investigated. The diameter and length of piles varied from 457 to 610 millimeters (18 to 24 inches) and from 12 to 25 meters (40 to 83 ft) respectively. The piles were socketed in clay-shale up to 7.5 diameter of the pile and the measured maximum loads from field tests varied from 1915 to 4000 kN (215 to 450 tons). The unconfined compressive strength (q_u) of clay-shale was in the range of 1300 to 2300 kPa (188 to 333 psi). The load-displacement relationships for the ACIP piles were predicted using a non-dimensional hyperbolic relationship and the model parameters were related to the rock properties and pile dimensions. For the ACIP piles socketed in clay-shale, 50% of the ultimate load was achieved in the displacement range of 0.005 to 0.012 of the diameter. Simple relationships have been developed to predict the pile capacity and model parameters based on unconfined compressive strength (q_u) of rock and Texas Cone Pentrometer (TCP) results.