Statnamic testing in clay soils

Tests have been carried out under different loading regimes on an instrumented model pile in order to gain a better understanding of Statnamic testing of piles in clay. The model pile was installed in an instrumented clay bed consolidated from a slurry, with known boundary conditions. Tests using a computer controlled servo-hydraulic actuator simulated static, constant rate of penetration (CRP) and Statnamic loading. It was demonstrated that the conventional nloading point method (UPM) of analysis for Statnamic tests requires modification to accommodate rate effects in clay soils. The viscous dampingthat occurred during loading could be represented by a non-linear power law incorporating damping coefficients. The model study was calibrated using a full-scale prototype instrumented auger bored pile in glacial lodgement till. Based upon full scale Statnamic testing on this pile, a class A prediction was madeof the equivalent static pile response using a modified model incorporating the non-linear viscous damping. Results from the prediction gave an ultimate static capacity which lay between maintained load test (MLT) and constant rate of penetration (CRP) tests. The pile's initial working zone stiffness duringCRP loading was higher than that predicted by the modified model and the UPM