The dynamic response of piles is a fundamental issue that significantly affects the performance of pile foundations under vertical cyclic loading, yet it has been insufficiently explored due to the limitations of experimental methods. To address this gap, a hydraulic loading device was developed for centrifuge tests, capable of applying loads up to 2.5 kN and 360 Hz. This device could simulate the primary loading conditions encountered in engineering applications, such as those in transportation and power machinery, even after the amplification of the dynamic frequency for centrifuge tests. Furthermore, a design approach for model piles that considers stress wave propagation in pile body and pile-soil dynamic interaction was proposed. Based on the device and approach, centrifuge comparison tests were conducted at 20 g and 30 g, which correspond to the same prototype. The preliminary results confirmed static similarity with only a 1.25% deviation in ultimate bearing capacities at the prototype scale. Cyclic loading tests, conducted under various loading conditions that were identical at the prototype scale, indicated that dynamic displacement, cumulative settlement, and axial forces at different burial depths adhered the dynamic similarity of centrifuge tests. These visible phenomena effectively indicate the rationality of centrifuge tests in studying pile-soil interaction and provide a benchmark for using centrifuge tests to investigate soil-structure dynamic interactions.

The mechanical response of energy pile groups in layered cross-anisotropic soils under vertical loadings is studied with the aid of the coupled finite element method- boundary element method (FEM-BEM). The single energy pile is simulated based on the finite element theory, which then is extended to energy pile groups. The global flexibility matrix for soils is obtained by considering the coupling effects of vertical and thermal loadings. The coupled FEM-BEM equation for the interaction between energy pile groups and soils is derived based on the displacement compatibility condition at the pile-soil interface. According to the displacement coordination condition and force balance in the rigid cap, the displacement of the cap and axial forces of pile groups can be solved. The presented theory is validated by comparing the calculated results with numerical simulations and field test results in existing literature. Finally, effects of the thermal loading, pile-soil stiffness ratio, pile spacing, cross-anisotropy of Young's modulus and the stratification are discussed.