A Finite Element Model for Investigating Unsteady-State Temperature Distribution and Thermomechanical Behavior of Underground Energy Piles

The underground energy geostructure represented by the pile is one of key paths for cooperative development space and geothermal energy. Because its advantages low cost, high efficiency no extra occupation space, it has become a feasible alternative to borehole heat exchanger. change in temperature field surrounding ground not only affects geological environment but also influences thermomechanical performance durability structure. However, temporal spatial unsteady-state distribution piles rock under typical intermittent unbalanced thermal load conditions still unclear. In this paper, finite element model was applied analyze distribution, behavior group developed verified. working were determined. Moreover, characteristics investigated. Finally, layout on identified designing six different scenarios. results indicate that operation conditions, near exchange pipe varies periodically. For areas with cooling heating loads, long-term leads accumulation, maximum occurs first daily cycle. summer/winter increase/decrease induces axial compression/tensile stress. When partially used as pile, non-energy acts “anchor pile”, generates added tensile