Study on the thermal response of spiral energy piles based on field test

Abstract

Field tests of spiral energy piles under the combined effect of temperature and loading are relatively few. Based on the field test, the heat transfer efficiency, pile strain, axial force and shaft friction of two spiral energy piles were studied. The major findings of the experimental studies were as follows: First, when the double spiral energy pile was heated, the temperature distribution was more uniform; the total heat transfer and the heat transfer rate were higher than those of the single spiral energy pile. Second, the pile strain distribution was such that smaller values were noticed at both pile ends while larger values were in the middle part of the pile. The additional tensile stresses of the two piles generated during cooling reached 4.06 MPa and 4.75 MPa, which exceeded the tensile strength of concrete. Finally, during heating, the shaft friction was negative in the middle and upper pile and positive in the middle and lower pile. The single spiral energy pile showed two neutral points. The downward load generated by the single spiral energy pile was about 885 kN higher than that generated by the double one. The above changes should be focused on in the actual project.