Thermal induced horizontal earth pressure changes of pipe energy piles under multiple heating cycles

Abstract

This paper explores the potential use of a pipe pile as a heat exchanger. The comparison between the thermomechanical characteristics of the solid energy pile and pipe energy pile was analyzed by using the model test method. The potential effects of thermal cycles on the horizontal earth pressure and the pile resistance redistribution were analyzed and discussed. Moreover, this paper also presents a preliminary investigation on the thermally induced contraction of the surrounding sandy soil. The results showed that the repeated expansion and contraction of energy piles would induce decreases in the horizontal earth pressure and impose an increased tip resistance to balance the shaft resistance reduction during the thermal cycles. Settlement would gradually accumulate at a reducing rate for the energy piles, and the accumulation of the pile settlement could be accompanied by the thermal contraction of the sandy soil. After three thermal cycles, the solid pile accumulated a 20% greater percentage of pile settlement than the pipe pile. However, the reduction in the shaft resistance of the pipe pile was larger than that of the solid pile. Hence, for the practical design of pipe energy piles, attention must be paid to the potential impact of thermal cycles on the pile structure.