This paper studies the time-dependent behavior of a pile drilled in layered saturated viscoelastic rock-soil mass due to a vertical load. By virtue of the finite element method (FEM), the pile is discretized into three-node axial bar elements. On the basis of the consolidation solution of layered transversely isotropic saturated rock-soil mass, the fractional Poyting-Thomson model and fractional Merchant model are used to simulate the rheological properties of rock and soil, respectively. The viscoelastic solution of layered saturated rock-soil mass under annular linear loads is derived according to the elastic-viscoelastic correspondence principle. Taking the above solutions as the kernel functions of the boundary element method (BEM), and combining with the stiffness matrix equation of a pile, a coupling formula of pile-soil-rock interaction is further established by the FEM-BEM coupling method. A MATLAB code is developed for numerical calculation, and the correctness of the present theory and calculation method are verified by comparing with the existing solutions, field tests and ABAQUS analyses. Finally, the key factors influencing the time-dependent behavior of piles are in-depth discussed.

This study investigates the interaction between energy piles and layered saturated soils, considering the consolidation induced by the thermal loads and mechanical loads. Initially, the coupled thermo-hydromechanical solution of layered media is obtained by utilizing the boundary element method (BEM) and the transformed differential quadrature method. Subsequently, the energy piles are discretized and modelled by the finite element method (FEM), and the solving equation for piles is established. To reflect the interaction between piles and soils, a coupled BEM-FEM matrix equation is formulated and solved by incorporating displacement coordination conditions and force equilibrium conditions. This approach facilitates the analysis of the temporal evolution of displacements and temperatures of piles and surrounding soils. The proposed methodology is validated through comparisons with monitoring data of field tests and results from simulations. Ultimately, the key factors, including the temperature increments, mechanical loads, length-diameter aspect ratio are examined through examples.