Analysis of a Static Loading Test on an Instrumented Cased CFA Pile in Silt and Sand

Abstract

A static loading test was performed on an instrumented 630 mm diameter, 12.5 m long, cased continuous flight auger (CFA) pile. The soil at the site consisted of a 4.0 m thick layer of loose sandy and silty fill layer underlain by a 1.6 m thick layer of dense silty sand and sand followed by dense sand to depth below the pile toe level. The instrumentation comprised vibrating wire strain gages at 1.0, 5.8, 9.4, and 12.0 m depth. The pile stiffness (EA) was determined by the secant and tangent methods and used in back-calculating the distributions of axial load in the pile. A t-z/q-z simulation of the test was fitted to the load-movement distributions of the pile head, gage levels, and pile toe. The load-movement response for the shaft resistance was strain-hardening. The records indicated presence of residual force. Correction for the residual force gave a more reasonable shaft resistance distribution and indicated an about 600 kN residual toe force.