It is generally accepted that the unit shaft resistance of piles in sands is lower for tensile loading than forcompressive loading. So far, very little attention has been paid to the influence of the installation methodon the tensile-to-compressive unit shaft resistance ratio. The objective of this paper is to analyze the effectof installation method on the ratio of unit shaft resistance in tension to that in compression for a model pileinstalled in a dense silica sand. To study installation effects, load tests on model piles were carried out in ahalf-cylindrical calibration chamber with digital image correlation (DIC) capability. The model piles wereeither jacked in one stroke using a constant rate of advance, or pre-installed into the dense sand samples.Digital images of the model pile and sand were taken during the load test and processed using DIC to obtainthe displacement field in the sand. It was found that unit shaft resistance was essentially the same in tensionand compression for the pre-installed pile, however for the jacked pile, the unit shaft resistance in tensionwas approximately half of that in compression. DIC analysis revealed that: (1) during the load test, moredisplacement occurs in the soil domain for the pre-installed pile compared to the jacked pile, (2) for thejacked pile, the magnitude of displacement in the soil domain is greater in tension than in compression and(3) for the pre-installed pile, the magnitudes of displacement in tension and compression are similar.
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