Model tests of energy piles with and without a vertical load

Abstract

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.

Axial and Radial Thermal Responses of a Field-Scale Energy Pile under Monotonic and Cyclic Temperature Changes

“…A number of small-scale physical model studies have characterized the axial thermal response of energy piles for monotonic heating (McCartney and Rosenberg, 2011;Ng et al, 2014b;Goode and McCartney, 2015) and cyclic temperatures (Kalantidou et al, 2012;Ng et al, 2014a;Stewart and McCartney, 2014;Yavari et al, 2014Yavari et al, , 2016aNg et al, 2016;Wang et al, 2016).…”

“…Another reason for the stable responses of the thermal strains towards the end of experiments is that there were no head loads on the pile or end restraints in the present study. According to some physical model studies with thermal cycles on energy piles (Kalantidou et al, 2012;Stewart and McCartney, 2013, Yavari et al, 2014, 2016aWang et al, 2016), thermally induced settlement is reversible for pile head loads corresponding to as low as 20% of the pile ultimate resistance, and becomes irreversible for higher pile loads, particularly for loads closer to the ultimate pile resistance. However, the soil type plays an important role in the thermal response of the pile, and the dense sand at the current site likely contributed to the relatively high resistance to axial thermal deformations.…”

Thermomechanical Behavior of Energy Pile Embedded in Sandy Soil

“…The comparison of load-settlement profile with Wang et al [22] was shown in Figure 7. The bearing capacities of the PEP and solid energy pile both decreased with the decreasing temperature.…”

FEM Analysis and Simplified Approach for a Single Energy Pile Subjected to Thermomechanical Loads

“…The change of energy pile bearing characteristic was subjected to the restraint conditions of the tested piles, and it was also found that the use of energy piles causes significant thermally induced additional deformation in the pile itself [7][8][9][10]. Model tests were also carried out to examine the heat transfer performance and bearing characteristics of piles with embedded tubes under normal working conditions over repeated temperature cycling, and the results show that the thermal stresses were superimposed with the mechanical stresses [11][12][13][14]. Centrifuge modeling of soilstructure interaction in energy foundations was also carried out to measure the transient thermomechanical response of end-bearing energy pile during heating-cooling cycles, and the result shown that the model pile was affected by the heating and cooling cycles [15,16], being consistent with the conclusion that the effect of temperature on the shear strength of sand, clay, and the clay-concrete interface is negligible [17,18].…”