Volume 30, Issue 3 (May 2007)
Rate-Controlled Lateral-load Pile Tests Using a Robotic Manipulator in Centrifuge
Robotic manipulators, as a new facility for centrifuge modeling, can provide a platform to carry out complex in-flight simulation of geotechnical problems. In this study, a four-axis robotic manipulator was employed to conduct a series of laterally-loaded pile tests in sand. Four model piles were installed into a sand bed and laterally loaded at different loading rates consecutively without stopping the centrifuge, which accordingly maximized consistency of the soil sample among the tests. Tests in both loose sand and dense sand were conducted. Detailed information of the test devices and procedures of soil sample preparation and load testing is described in this paper. The test results, including horizontal force-displacement curves, bending moment distributions, relationships between lateral resistance and loading rates, and p-y curves derived from the measured bending moment distributions, are presented. In addition, the effects of loading rate and ground surface are discussed based on the test results. It is found that, under the investigated conditions, loading rate has little effect on the horizontal resistance at specified displacements, but has significant effects on the bending moment and soil reaction distributions. The ground surface also has an effect on the behavior of the laterally-loaded piles. A simple modification method is used to consider the effect of ground surface on p-y curves at shallow depths.