A Novel Method to Predict Shaft and Base Responses of a Pile from Cyclic Pile Load Test Results

Abstract The ultimate capacity of the pile foundation is estimated using criteria such as overburden pressure and the strengths and unit weights of the soil layers. The assessment of a pile's axial capacity entails a great deal of uncertainty in choosing the right design parameters, and design...
Ausführliche Beschreibung

Abstract The ultimate capacity of the pile foundation is estimated using criteria such as overburden pressure and the strengths and unit weights of the soil layers. The assessment of a pile's axial capacity entails a great deal of uncertainty in choosing the right design parameters, and design principles aren't always in accordance with the processes/procedures involved in installation. The estimated capacity may differ with actual one as values of strength, stiffness, interface resistance between pile and soil and lateral earth pressure coefficient with depth and soil stratification could be different from the values estimated from prior testing or assumed. An initial monotonic or cyclic pile load test is often performed to validate the predicted capacity. Validation often involves ascertaining the design estimate even if the observed settlement at the design load is very small. No attempt was made to evaluate ultimate or design shaft and base resistances. It is possible to estimate the same in some limited cases from the cyclic pile load tests but rarely are those validated. Due to the aforementioned discrepancies of usual practice, a novel method for back-analyzing and estimating ultimate base and shaft resistances, as well as initial stiffnesses of the shaft and base of the pile, based on the load–displacement response from monotonic or cyclic pile load tests, is presented. The topic is momentous as current design methods often largely underestimate the capacity of piles, resulting in an over-conservative design. The proposed approach permits verification of the a-priori predictions based on geotechnical parameters, geometry (shape, length and diameter), construction methodology and other uncertainties involved at site during installation of the pile. The proposed approach is based on an iterative procedure by deploying hyperbolic relationships for the nonlinear responses of shaft and base resistances of the pile response. The pile–soil system is modeled in terms of Winkler model with different nonlinear responses for the shaft-soil and base resistances. The capability of the procedure to predict shaft and base stiffnesses and ultimate shaft and base resistances is checked against data from full-scale cyclic pile load test for validation. Ausführliche Beschreibung