Centrifuge Modeling of End-Restraint Effects in Energy Foundations

• Published in: Journal of geotechnical and geoenvironmental engineering 2015-08, Vol.141 (8)
• Main Authors: Goode, J. C, McCartney, John S
• Format: Article
• Language: English
• Subjects: Technical Papers
• ISSN: 1090-0241; 1943-5606
• DOI: 10.1061/(ASCE)GT.1943-5606.0001333

AbstractThis study presents the results from physical modeling experiments on centrifuge-scale energy foundations in dry sand and unsaturated silt layers. These experiments were performed to characterize end restraint effects on soil-structure interaction for energy foundations in different soils and include tests on foundations with semifloating and end-bearing toe boundary conditions and free-expansion and restrained-expansion head boundary conditions. Two scale-model energy foundations having different lengths were constructed from reinforced concrete to simulate end-bearing and semifloating conditions in soil layers having the same thickness. The foundations include embedded thermocouples and strain gauges, which were calibrated under applied mechanical loads and nonisothermal conditions before testing. The variables measured during the experiments include axial strain and temperature distributions in the foundation, temperature, and volumetric water content measurements in the soil, vertical displacements of the foundation head and soil surface, and axial stress at the foundation head. These variables were used to calculate the distributions in thermal axial stress and thermal axial displacement, which are useful in evaluating soil-structure interaction mechanisms. The results confirm observations from full-scale energy foundations in the field for end-bearing foundations and provide new insight into the behavior of semifloating foundations. Heating of the semifloating foundations in compacted silt led to a clear increase in ultimate capacity, potentially due to changes in radial normal stress and thermally induced water flow, while heating of the semifloating foundations in dry sand led to a negligible change in ultimate capacity.