Investigations of pile–soil interaction under thermo-mechanical loading

Abstract

Thermo-active piles that couple load bearing with ground source heat pump systems are one of the new technologies in geotechnical engineering. This paper investigates the pile–soil interaction behaviour of a thermo-active pile in overconsolidated London clay by conducting a thermo-hydro-mechanical finite element analysis using an advanced soil constitutive model. Negative and positive excess pore pressures are computed around the pile during cooling and heating, respectively. However, the difference in the radial effective stress acting on the pile–soil interface between the cooling and heating stages is small, and the pile–soil interaction is governed by the shear mobilization associated with thermally induced cyclic movements of pile expansion and contraction. During the first cooling stage, the shear stress at a small portion in the upper part of the pile reaches close to the yield values, which leads to an additional settlement about 3 mm from the original mechanical load–induced settlement of 2 mm. The shear stresses in subsequent heating and cooling cycles are much smaller than the ultimate shear stress values, because of the heavily overconsolidated nature of the London clay.

Finite element modeling of thermo-active diaphragm walls

“…This value is close to the value suggested by Bourne-Webb et al [5,7]. The CTE of pore water α w is 70 µε/°, the porosity n in this case study is assumed 0.3, and other thermal properties about C sw and l are from Rui and Yin [19,23], Rui et al [24], Rui and Soga [20].…”

“…A large number of studies have been performed investigating the effects of the operation of the thermoactive piles on the structural performance of the foundations [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Some other work focuses on the coupled thermo-hydro-mechanical behavior of energy storage [21].…”

“…This paper follows the work by Rui and Yin [19], which focused on the discussion of pile-soil interaction under both thermal and mechanical loading. In the present paper, this issue is explored further by thermo-hydro-mechanical coupling finite element analysis (FEA).…”