Analytical solution for transient radial interaction between energy piles and soils: Thermo-elastic cavity expansion analysis

Bearing capacity of energy piles may be affected by the Radial Interaction between Energy Piles and Soils (RIEPS) such as energy pile expansion and transient radial heat conduction. This paper proposes a cavity-expansion-based solution to investigate the thermo-elastic RIEPS. Transient temperature distributions are shown by assuming heat conduction in the radial direction and constant temperature at the pile-soil interface. With the temperature distributions, a thermo-elastic solution is obtained to capture the changes in stresses and displacements around energy piles. It is found that the solution under the combined thermal-mechanical loading pattern is the linear superposition of those under the thermal loading and mechanical loading patterns. Hence, the stresses, strains and displacements in soils are determined by the competitive relationships between thermal and mechanical loading patterns. The expression for radial stress change at the pile-soil interface is discussed by the cavity expansion analysis and comparison with field data. For typical soil and pile parameters, the expression could be quite general considering transient temperature distributions and soil/pile moduli. This paper can benefit to the capacity design of energy piles by taking the RIEPS into account.