Experimental and simulation study on the thermal-mechanical performance of phase change energy pile

Phase change materials are incorporated into concrete to create phase change pile storage concrete, significantly enhancing the heat transfer efficiency of energy piles. However, adding these aggregates reduces concrete strength. This research examines how different proportions of steel balls, silicon carbide powder, and steel fibers affect the thermal and mechanical properties of pile foundation concrete. An orthogonal test under compressive design strength shows that a mix of 9% silicon carbide powder, 0.7% steel fiber, and 15% steel balls increases thermal conductivity by 25.3%. Numerical simulations with this optimized ratio indicate a 21% increase in heat transfer per unit depth compared to standard energy piles. The phase change energy pile notably lessens thermal effects on soil. Within 30 days of operation, its thermal influence radius decreased by 11.9%. Furthermore, maximum reductions in side friction, pile side stress, and displacement were recorded at 95.9%, 59.1%, and 80.3%, respectively, demonstrating excellent structural stability.