Department of Transportation and Geotechnical Engineering

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Browsing Department of Transportation and Geotechnical Engineering by Subject "Cyclic loading"

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    Advanced Laboratory Investigation of Axial Cyclic Loading in Silica Sands
    (2015) Tsuha, Cristina de H. C.; Jardine, Richard J.; Yang, Zhongxuan X.; Silva, M.; Rimoy, Siya P.
    This paper describes the global behaviour of and local stress conditions applying to highly instrumented cyclic laboratory model displacement pile tests conducted in a calibration chamber on medium dense Fontainebleau NE34 sand. The instrumentation provided measurements of the contact stresses on the jacked pile shaft and the local vertical, radial and circumferential stresses in the surrounding soil mass, in tests involving a range of cyclic load amplitudes. The patterns of effective stress developing on and around the pile shaft are described. The data obtained are interpreted by reference to cyclic soil element tests conducted on the same soil, as described in the parallel investigation by Aghakouchak et al (2015), reported in the same symposium. The calibration chamber experiments offer a comprehensive understanding of the cyclic degradation processes, and provide key information for improving the design of piled foundations under cyclic loading.
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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.