Department of Transportation and Geotechnical Engineering

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Browsing Department of Transportation and Geotechnical Engineering by Author "Jardine, R. J."

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    Behaviour of Displacement Piles in Sand under Cyclic Axial Loading
    (Elsevier, 2012) Tsuha, Cristina de H. C.; Foray, P. Y.; Jardine, R. J.; Yang, Zhongxuan X.; Silva, M.; Rimoy, Siya P.
    Field experiments have demonstrated that piles driven into sand can respond to axial cyclic loading in Stable, Unstable or Meta-Stable ways, depending on the combinations of mean and cyclic loads and the number of cycles. An understanding of the three styles of responses is provided by experiments involving a highly instrumented model displacement pile and an array of soil stress sensors installed in fine sand in a pressurised calibration chamber. The different patterns of effective stress developing on and around the shaft are reported, along with the results of static load tests that track the effects on shaft capacity. The interpretation links these observations to the sand's stress–strain behaviour. The interface-shear characteristics, the kinematic yielding, the local densification, the growth of a fractured interface-shear zone and the restrained dilatancy at the pile–soil interface are all found to be important. The model tests are shown to be compatible with the full-scale behaviour and to provide key information for improving the modelling and the design rules.
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    Stresses Developed around Displacement Piles Penetration in Sand
    (American Society of Civil Engineers, 2013-08-16) Yang, Zhongxuan X.; Jardine, R. J.; Zhu, B. T.; Rimoy, Siya P.
    Establishing the stress conditions developed around displacement piles in sands is crucial to improving the understanding and modeling of their behavior. High-quality experiments and theoretical analyses are providing new insights into the effects of penetration on stress conditions. This paper synthesizes the findings from three independent experimental studies on normally consolidated silica sands and a trio of numerical analyses that tackle the problem from different perspectives. The significant degrees of uncertainty in the measurements and predictions are recognized and significant differences between data sets are discussed and largely resolved. Applying a consistent normalized interpretive framework leads to clear common trends regarding how installation affects the stress regime. While the main emphasis is placed on the radial effective stresses developed around pile shafts, the circumferential and vertical stress states are also considered.