## 1 Introduction
They  
Figure 1: Detailed drawing comparing IBP-EP and DBP-EP. validated the feasibility of indoor modeling tests by considering various thermomechanical parameters, such as loading conditions, operational modes, pile material, and layout configurations. [PERSON] et al. [37] conducted comparative modeling tests on IBP-EP and improved energy piles and discovered that pre-burying heat exchanger tubes within steel tubes has a minimal impact on the structural safety of the piles, but it reduces their heat exchange capacity. [PERSON] et al. [38] and [PERSON] et al. [7] performed modeling tests on helical energy piles to investigate their thermomechanical behavior under both summer and winter conditions. [PERSON] et al. [19] and [PERSON] et al. [20] conducted thermomechanical response tests on static drill rooted energy piles using modeling tests that considered the surrounding soil and the effects of different heating methods. [PERSON] et al. [8] carried out field tests on PHC energy piles to examine their thermomechanical behavior under various operational conditions. [PERSON] et al. [39] studied the effects of asymmetric thermal loading on energy pile groups over long-term operation by modeling a three-dimensional energy pile group. They analyzed the pile-soil-slab interaction by comparing the ratios of thermal expansion coefficients, pile-soil stiffness, and slab-soil stiffness. [PERSON] et al. [40; 41] found that multiple cycles of heating and cooling cause continuous accumulation of pile settlement, as demonstrated through their modeling experiments. Mechanical loading also influences the thermomechanical behavior of energy piles. [PERSON] et al. [42] performed thermomechanical response experiments on energy piles situated in dry sand via modeling tests, revealing that heating the tops of the piles while maintaining constant axial loads leads to bulging and causes irreversible settlement at the tops. In a separate study, [PERSON] et al. [43] explored the thermomechanical performance of energy piles subjected to prolonged inclined mechanical loads by creating a three-dimensional model. [PERSON] et al. [44], along with [PERSON] et al. [45] and [PERSON] et al. [46], executed thermomechanical response experiments on energy piles using indoor models, which considered a range of operating conditions, constraints, and soil parameters. [PERSON] et al. [47] investigated the horizontal bearing behavior of energy piles within sandy soil through modeling tests and found that both heating and cooling elevate the soil pressure in front of the piles. [PERSON] et al. [48] assessed the load-displacement response of energy piles via numerical simulations to evaluate alterations in their bearing capacity. [PERSON] et al. [49] formulated a three-dimensional model for an energy pile group subjected to vertical loading in saturated soil, examining how pile spacing, arrangement, loading duration, soil layering, and the modulus ratio of the soil skeleton affect the thermomechanical behavior of the pile group. The research indicates that mechanical load significantly influences the thermomechanical behavior of energy piles during the heating process. The application of mechanical loads complicates the study of the thermomechanical behavior of energy piles, so more thermal response tests on energy piles should be carried out. The above analysis indicates that the changes in the thermomechanical behavior of DBP-EP during the heating process are complex due to the combined effects of temperature and mechanical loads. To investigate this thermomechanical behavior, this paper establishes a single-pile model test for DBP-EP and conducts thermomechanical response tests on a single DBP-EP pile. To achieve a more precise simulation of real working conditions, a steady load is applied to the upper section of the pile, while circulating water is introduced during the testing phase.