Evolution of local friction along a model pile shaft in a calibration chamber for a large number of loading cycles

Bekki, Hadj; Canou, Jean; Tali, Brahim; Dupla, Jean Claude; Bouafia, Ali

doi:10.1016/j.crme.2012.11.012

Cited by 22 publications

(9 citation statements)

References 21 publications

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“…The vertical stress is applied to the specimen by applying a water pressure, p conf,v , through a large diameter bottom piston and the horizontal stress is applied, independently, through a water pressure, p conf,h , which horizontally confines the specimen contained in a neoprene membrane. For sand testing, a comprehensive description of the equipment and associated testing procedure has been given by Bekki et al (2013) and more details will be found in that paper.…”

Section: The Calibration Chamber Testing Setupmentioning

confidence: 99%

“…Different authors (Tali 2011;Bekki et al 2013;Muhammed 2015) have defined and used a coefficient of friction evolution C e,fs , as defined below, in order to easily quantify the evolution of local friction during cyclic loading and to make an easy distinction between degradation phases, corresponding to a decrease of C e,fs and reinforcement phases, corresponding to an increase of this coefficient, with respect to the initial mobilization of friction observed on the first cycle. In the present work, the coefficient of evolution has also been adopted in order to further analyse and quantify the evolution of local friction behaviour during the cyclic sequence.…”

Section: Analysis Of the Cyclic Sequencementioning

confidence: 99%

“…Concerning the case of very large numbers of cycles (several 10 4 to 10 6 cycles, corresponding to fatigue behavior), very few if no publications are available. For sands, Bekki et al (2013) have presented results showing the evolution of local friction along an instrumented pileprobe jacked into a sand specimen reconstituted in a calibration chamber, for large numbers of displacement-controlled cycles (10 5 cycles). The results obtained show that after an initial degradation phase of the local skin friction (cyclic strain-softening), a reinforcement phase D r a f t 4 (cyclic strain-hardening) develops up to very high number of cycles (10 5 ).…”

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confidence: 99%

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Evaluation of local friction and pore-water pressure evolution along instrumented probes in saturated clay for large numbers of cycles

et al. 2019

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In order to investigate local friction mobilization along piles submitted to cyclic axial loadings, a calibration chamber experiment is presented based on the implementation of instrumented probes in specimens of saturated clay. Typical results obtained with a piezoprobe are presented, allowing to measure, on top of tip resistance and local friction, the local pore water pressure (PWP) developed on the probe shaft. Specific piezometers installed in the clay specimen allow, in addition, to obtain a good picture of the PWP field around the probe during installation and loading.After installation of the probe, a succession of monotonic and cyclic displacement-controlled loading phases are applied. Upon cyclic loading of the piezo-probe up to very large number of cycles (10 5 cycles), an initial degradation of local friction is observed, followed by a subsequent reinforcement, which keeps going until the end of the cyclic sequence. The friction evolution is related to the evolution of the PWP measured during cyclic loading. In particular, the influence of the cyclic loading sequence on the post-cyclic static friction resistance is evaluated. A comparison is finally made with the results obtained with another type of probe, showing a good consistency between both types of results.

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Section: The Calibration Chamber Testing Setupmentioning

confidence: 99%

Section: Analysis Of the Cyclic Sequencementioning

confidence: 99%

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confidence: 99%

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Evaluation of local friction and pore-water pressure evolution along instrumented probes in saturated clay for large numbers of cycles

et al. 2019

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“…Grenoble Alpes interface were linked to shaft friction evolution during cycles. After a degradation phase observed by several authors, an increase in skin friction was measured by Bekki et al [4] for high number of cycles (between 100 and 100 000 cycles). These phenomena were attributed to the formation of a shear band of crushed grains around the shaft and a sand densification around the probe.…”

Section: Introductionmentioning

confidence: 83%

Effects of a large number of cycles on pile shaft resistance analyzed at the grain scale using x-ray tomography

et al. 2017

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This study presents the results of laboratory-scale cyclic loading tests performed on an instrumented pile in sand using x-ray micro tomography and three-dimensional (3D) image analysis techniques. The macroscopic behaviour of sand-pile interface shows a two−phases evolution during cycles with a non negligible increase of shaft friction in the second phase. A discrete version of Digital Image Correlation (DIC) is employed to analyze quantitatively the mechanisms occurring at the grain scale. Using segmented images this method is able to correlate and follow each grain individually between two configurations. Displacement fields are measured and compared for different amounts of cycles. Grain breakage and density evolution are investigated using grey level measurements. The results provide a better understanding of the phenomena observed at the macroscale for a high number of load cycles.

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“…Le Kouby et al [9] and D' Aguiar et al [10] found that the bearing capacity of a pile would be significantly improved when the amplitude of any cyclic loading was optimised. Bekki et al [11] indicated that the side friction on a pile would show strain hardening because of the phenomenon of shear dilatancy under a large number of cycles. Chen et al [12] and Ren [13] studied the cyclic performance of pile foundation subjected to long-term axial cyclic loading in silt.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Behaviours of a Single Soft Rock-Socketed Shaft Subjected to Axial Cyclic Loading

Zhang

Huang

Mei

et al. 2016

Advances in Materials Science and Engineering

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The soft rock was simulated by cement, plaster, sand, water, and concrete hardening accelerator in this paper. Meanwhile, uniaxial compressive strength tests and triaxial compression tests were conducted to study the mechanical properties of simulated soft rock samples. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted by using a device which combined test apparatus with a GCTS dynamic triaxial system. Test results show that the optimal mix ratio is cement : plaster : medium sand : water : concrete hardening accelerator = 4.5% : 5.0% : 84.71% : 4.75% : 1.04%. The static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation and cyclic secant modulus of the pile head. The accumulated deformation increases with increasing numbers of cycles. However, the cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles and finally remains stable after 50 cycles. According to the test results, the development of accumulated settlement was analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio, and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to traffic loading.

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Evolution of local friction along a model pile shaft in a calibration chamber for a large number of loading cycles

Cited by 22 publications

References 21 publications

Evaluation of local friction and pore-water pressure evolution along instrumented probes in saturated clay for large numbers of cycles

Evaluation of local friction and pore-water pressure evolution along instrumented probes in saturated clay for large numbers of cycles

Effects of a large number of cycles on pile shaft resistance analyzed at the grain scale using x-ray tomography

Dynamic Behaviours of a Single Soft Rock-Socketed Shaft Subjected to Axial Cyclic Loading

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