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The main causes of soil setup effects on pile response are generation of excess pore water pressure (EPWP) due to installation of prefabricated piles in saturated soils and subsequent dissipation of EPWP and, hence, stress state variations around the pile shaft. The main objective of this paper is evaluating the effects of pile diameter and over-consolidation ratio (OCR) on variations of stress state in soil adjacent to the pile and variations of the pile ultimate load over time using a nonlinear finite-element method numerical scheme and comparisons with field test data. The numerical model involves simulation of the pile penetration throughout the installation process and, hence, simulation of EPWP inducement and its dissipation over time during consolidation. The field data include pile driving and load test data in normally consolidated (soft) and overconsolidated (stiff to very stiff) fine-grained strata. The results have shown that the ratio of EPWP dissipation to overconsolidation stress reduces with an increase of OCR. The coefficient of lateral soil pressure has also increased with OCR and pile diameter. A "setup ratio" is defined as the ratio of shaft resistance at the end-of-consolidation to end-of-drive and is shown to have a proportional relationship with the pile diameter and a nonlinear and reducing trend with an increase in OCR. Correlations are proposed to modify existing relations for an increase in shaft resistance with time, incorporating OCR and pile diameter as well. Finally, the field data interpretations of a site having sufficient pile-load testing data in normally and overconsolidated fine-grained stratifications have validated the findings of the numerical model. [ABSTRACT FROM AUTHOR]

In this study, a relationship between small-strain shear modulus (Gmax) and overconsolidation ratio (OCR) based on shear wave velocity (Fs) measurement was established to identify the stress history of centrifuge model ground. A centrifuge test was conducted in various centrifugal acceleration levels including loading and unloading sequences to cause various stress histories on centrifuge model ground. The Vs and vertical effective stress were measured at each level of acceleration. Then, a sensitivity analysis was conducted using testing data to ensure the suitability of OCR function for the tested cohesionless soils and found that OCR can be estimated based on Vs measurements irrespective of normally-consolidated or overconsolidated loading conditions. Finally, the developed Gmax-OCR relationship was applied to centrifuge models constructed and tested under various induced stress-history conditions. Through a series of tests, it was concluded that the induced stress history on centrifuge model by compaction, g-level variation, and past overburden load can be analysed quantitatively, and it is convinced that the OCR evaluation technique will contribute to better interpret the centrifuge test results. [ABSTRACT FROM AUTHOR]

This paper reports K0 of dry sand in response to different loading conditions and under secondary compression. The experiments were carried out using an oedometer and tactile pressure sensors were used to measure the horizontal stress for K0 calculations. During loading, K0 remains a constant as the vertical stress δ′v increases. The corresponding discrete element method (DEM) simulations reproduced this experimental finding and suggest that the force transmission pattern is similar and the contact forces among particles are proportionally increased in both the horizontal and vertical directions to give a constant K0 as δ′v increases. K0 increases as the overconsolidation ratio (OCR) increases during unloading because of the locked-in horizontal stress. Reloading makes the sample less sensitive to OCR and thus the sample behaves as if it were in a normally consolidated state where K0 is a constant. Experimental results and DEM simulations demonstrate that the horizontal stress δ′h and K0 continue to increase during secondary compression on the loading path. Secondary compression is initiated by creep at particle contacts and exhibits similar responses like primary creep. The subsequent loading after secondary compression can gradually bring K0 back to its initial value. During secondary compression on the unloading path, however, K0 continues to decrease according to the DEM simulation results. The creep process tends to relax the locked-in horizontal stress and the sample expands in the vertical direction. Therefore, δ′h and K0 gradually decreases. [ABSTRACT FROM AUTHOR]