Interaction analysis of energy pile group and layered transversely isotropic saturated soils under vertical loading

Studying the interaction between energy piles and saturated soil can provide guidance for the design, construction, operation, and maintenance of energy piles in soft soil areas. In this paper, the interaction between energy pile groups and layered transversely isotropic saturated soils under vertical loading is investigated based on the coupled FEM-BEM method. Firstly, the stiffness matrix equations of pile group are established by discretizing each pile with rod elements. Subsequently, the boundary of saturated soils is discretized to obtain the flexibility matrix of soils under thermo-mechanical loads. Then, by introducing displacement coordination conditions at the interface between piles and soils, as well as force balance conditions at the cap, the solution to the thermo-mechanical response of energy pile group in layered transversely isotropic saturated soils is obtained. Based on the theoretical derivation, MATLAB programs are developed, and the calculation results are compared and verified with the finite element software to demonstrate the efficiency and correctness of the work in this paper. Finally, effects of factors such as the pile spacing, arrangement of the pile group, time of loading application, soil stratification, and the ratio of soil skeleton modulus on the vertically loaded energy pile groups in saturated soils are analyzed.