Model pile behavior in calibration chamber under very large number of cycles of axial loading in saturated clay

ABSTRACT

The results of a series of displacement-controlled cyclic axial loading tests of model pile in saturated kaolinite clay, carried out in a calibration chamber, are presented. An instrumented pile-probe was used to investigate the evolution of local skin friction and excess pore water pressure during cyclic loading. After a brief description of the experimental setup and the testing procedure, the tests results are presented concerning the response of the probe during installation, initial monotonic axial loading, cyclic loading up to large numbers of cycles (10⁵ cycles) and post-cyclic monotonic axial loading. During cyclic loading, an initial degradation phase of local skin friction followed by a stabilization phase is observed. Generation of excess pore water pressure occurs during the 60 first cycles followed by a dissipation phase. Parametric study showed that, for initial monotonic loadings, maximum tip resistance and local skin friction are proportional to stress level. Furthermore, excess pore water pressure generated during cyclic loading depends both on initial stress level applied to the clay specimen and cyclic displacement amplitude. A peak value of local skin friction resistance has been observed during post-cyclic monotonic loadings.

KEYWORDS:

• pile-probe
• cyclic loading
• calibration chamber
• saturated clay
• local skin friction
• large number of cycles
• excess pore water pressure

Acknowledgements

The first author acknowledges the scholarship program PROFAS B+ 2015/2016 provided by the algerian and french governments. The authors would also like to thank the many persons within Navier Labortory staff at ENPC (France) for comments and assistance during experimental program.