Model tests of energy piles with and without a vertical load

The thermomechanical behaviour of energy piles during heating and cooling through model tests was studied. These model tests were carried out both with and without a vertical load and dry sand was used. The axial load distribution, load-settlement of the pile head, pile and soil temperature, soil pressure at the pile tip, horizontal soil pressure, thermal stress and mobilised side shear stress were investigated. The magnitude of stress and displacement influenced by vertical load or no load was comparatively analysed. The results show that heating and cooling induced thermal stress in piles and residual thermal stress was introduced after a heating and cooling cycle. Horizontal soil pressure also varied and changes in soil pressure at the pile tip differed depending on whether or not a vertical load was applied. Moreover, the pile temperature and the temperature within one pile diameter of the pile axis varied noticeably in the condition of this paper. The heave under no load was 143% of that under a vertical load after heating, while the settlement under no load was only 64% of that under vertical load after cooling.