Thermomechanical performance of energy retaining pile influenced by surrounding utility tunnel via the regression tree model

Abstract

The thermomechanical performance of energy retaining pile differs from that of axisymmetric energy pile due to utility tunnel excavation. This study presents four field tests of energy retaining pile conducted before and after utility tunnel construction. A regression tree (RT) model for predicting the thermally induced stress of energy retaining pile was established based on the measured water temperature, pile temperature and previous stage thermally induced stress to evaluate the effect of shallow buried utility tunnel on the thermomechanical performance of adjacent energy pile. The established thermally induced stress RT prediction model could acceptably predict the thermally induced stress of the future short-team. Surrounding utility tunnel excavation alters the distribution of the axial thermally induced stress. The axial thermomechanical response of the energy retaining pile after utility tunnel construction is approximately 50% that before utility tunnel construction. The asymmetrical boundary conditions cause a limited bending moment of the energy retaining pile at the top or bottom of the utility tunnel, which is not enough to threaten the pile safety. Moreover, the thermal performance of the energy retaining pile slightly increases due to the heat exchange between the pile and the air in the surrounding utility tunnel.