A Parametric Study on the Evolution of Cyclic Clay-Pile Interface Friction for Large Numbers of Cycles
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ORIGINAL PAPER
A Parametric Study on the Evolution of Cyclic Clay-Pile Interface Friction for Large Numbers of Cycles Rawaz Dlawar Muhammed Alain Tabbagh
. Jean Canou . Jean-Claude Dupla .
Received: 14 August 2019 / Accepted: 18 May 2020 Springer Nature Switzerland AG 2020
Abstract The present experimental study investigates the influence of cyclic displacement amplitude and effective consolidation stress on the evolution of mobilized local shaft friction along piles submitted to large number of cycles (up to 105 cycles). Two-way cyclic displacement-controlled tests were performed on an instrumented pile-probe installed and loaded in a calibration chamber. Tests were performed on reconstituted specimens of saturated clay to examine the shaft friction evolution in the soil-pile interface during cyclic loading. Displacement-controlled static tests were also performed before and after the cyclic loading in order to quantify the influence of cyclic parameters on post-cyclic static response. It was found that the amplitude of cyclic displacement and the initial state of stress have an influence on the evolution of local friction during cyclic loading. The degradation rate of local friction increased for larger cyclic displacement amplitudes whereas with increasing the effective consolidation stress, the degradation rate decreased. The application of displacement- controlled cycles resulted in a modification in the behaviour of the interface. A significant peak of static R. D. Muhammed (&) J. Canou J.-C. Dupla Navier Laboratory, Ecole Des Ponts ParisTech, 77420 Marne-La-Valle´e, France e-mail: [email protected] R. D. Muhammed A. Tabbagh Sorbonne Universite´, CNRS, EPHE, UMR7619 Me´tis, 75005 Paris, France
friction followed by strain softening was observed during post cyclic static tests, which was not the case for pre-cyclic static tests. The peak value of friction obtained upon post-cyclic static loadings found to be more important for higher values of applied displacement amplitude during cyclic loading. Finally, a brief synthesis of the results is given. Keywords Pile behavior Local shaft friction Amplitude of cyclic loading Frequency Confining effective stress Saturated clay Physical modelling Instrumented pile-probe
1 Introduction During their lifetime, pile foundations are often subjected, in addition to permanent static loads, to variable transient loadings, which will sometimes modify their bearing capacity. These complex loadings, often identified under the term of ‘‘cyclic loadings’’, can be characterized by various parameters like the amplitude of the cycles, their frequency, regularity, number of cycles, length of the sequences, etc. Understanding the behavior of piles submitted to such cyclic loadings constitutes an important aspect to be taken into account in the design of pile foundations. Over the past few decades, this subject has attracted considerable scientific interest and numerous research work has been published focusin
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