Statistical Uncertainty of Cyclic Resistance of Sand under Constant Volume Direct Simple Shear

Abstract

In the design work of offshore foundations, such as monopiles and gravity platforms, the cyclic resistance of soil plays a critical role in assessing the effect of cyclic loading induced by wind, waves, and rotor dynamics during the operational lifetime. However, the cyclic behaviour of soil is often derived from only a limited number of laboratory tests, which can lead to inaccurate estimates of soil behaviour. Furthermore, this imprecision can affect the parameters selection for the design process. To gain a better understanding of the limitations and uncertainties associated with laboratory experiments, a series of cyclic direct simple shear (cDSS) tests are conducted on marine sand. Four combinations of consolidation stress and void ratio are selected, and a constant volume cDSS test is repeated a substantial number of times for each combination. This dataset captures the measurement uncertainty on the cyclic soil resistance. By analysing the variability of the results, the statistical distributions for the cyclic soil resistance parameters can be determined (e.g. number of cycles to reach a certain shear strain level). The same specimen exhibits slightly different strain-stress relationships due to the inherent variability of sand. Statistical methods are used to describe the cyclic resistance of the sand.

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