Predicted and Observed Axial Behavior of Piles: Results of a Pile Prediction Symposium

This publication presents the results of a pile capacity event that was held at the Lakefill site on the Evanston Campus of Northwestern University in conjunction with the 1989 Foundation Engineering Congress. The event involved a series of axial load tests that were conducted on a hp 14×73 pile, a closed-ended pipe pile, a drilled pier installed using the slurry method, and a drilled pier installed with a temporary casing. The 50-ft-long piles were installed through 23 ft of dense sand overlying medium stiff clay. Based on in situ, laboratory, and geotechnical site characterizations; pile installation data; and load testing schedule, twenty-three a priori predictions of response were made. Predicted responses for tests conducted at two, five and forty-three weeks after installation included axial capacity, load distribution along the length of each pile at failure, axial load-pile head settlement, and lower bound estimates of capacity with 90% confidence that actual value would be higher than this lower bound. Predictions of residual load and pore pressure generation and dissipation were also made. These papers present the data upon which all predictions were based; describe methodologies and judgments used to make the predictions; present the results of the load tests, and summarize the predictions and compare predicted responses with observed behavior.