Centrifuge model tests on installation of suction caissons in sand

Abstract

When suction caissons are installed in sand layer, upward seepage flow occurs within sand due to the generation of hydraulic gradient. Upward hydraulic gradient (and hence upward seepage flow) significantly reduces the soil resistance and facilitates the caisson installation. However, this can create significant plug loosening and uplift the sand plug inside the caisson. However, the behavior of seepage flow and soil plug heave during suction installation are not yet fully understand. Therefore, this study aims to investigate the soil behavior during suction installation of caissons in sand and its influence on the installation process using the centrifuge model tests. To investigate the effect of suction installation on soil behavior, two types of centrifuge model tests were designed: half-section model test and total-section model test. From the half-section model test, the mechanism of sand heave formation was analyzed using image based technique. In the total-section model test, variation of suction pressure which was directly related with seepage flow was assessed. CPT tests were also conducted after removing the suction-installed caisson and found the evidence of soil plug loosening. The results emphasize the effect of soil plug loosening not only for the installation but also for the further performance.