Centrifuge model study on pile subject to lapses during installation in sand

Abstract

A series of centrifuge model tests has been carried out to investigate the behaviour of pile subject to lapses during installation in sand. To simulate an installation lapse, an instrumented model pile is jacked to a desired depth in sand, then allowed to rest for a desired duration before being jacked deeper into the sand during centrifuge flight. The test results reveal that the pile experienced a reduction in penetration resistance between the end of initial installation and the beginning of reinstallation. The magnitude of reduction in pile penetration resistance is noticeable even for short lapse duration and increases with the duration of installation lapse. However, the rate of reduction in resistance attenuates rapidly with time. The changes in the soil and pile stresses observed from instruments installed in the sand and along the pile shaft reveal that stress reduction has taken place around the pile tip and along the lower pile shaft. To further examine the observations, modified one-dimensional compression tests were carried out to monitor the stress changes in sand that is not allowed to settle once the desired loading pressure is reached. The test data reveal that stress reduction in. sand around the pile tip and along the lower pile shaft is a cause for the reduction in pile penetration resistance during an installation lapse.