Abstract: The Abel dashpot is introduced to improve the classical three-parameter Merchant model, and a fractional Merchant model which can better describe the viscoelastic characteristics of soils is obtained. With the help of finite element method, the pile group is discretized into single piles and pile elements. The total stiffness matrix equation of the pile group can be obtained by assembling the pile elements simulated by the Timoshenko beam model. According to the interaction equation between soils and the pile group, and the equilibrium condition and the compatibility condition of the pile cap, the matrix solution of the shear force at the top of the single pile and the displacement of the pile cap is deduced. Combined with the elastic-viscoelastic correspondence principle and the Laplace inverse transformation, the problem of the interaction between fractional viscoelastic saturated soils and laterally loaded pile groups is finally solved. Taking a set of creep test data as an example, this paper briefly introduces the specific method to obtain the viscoelastic parameters of the fractional model through the creep curve. The correctness of the proposed solution is verified by comparing with the published results and ABAQUS numerical examples. Additionally, several examples are designed to discuss the effects of soil’s viscoelasticity parameters on the stress and deformation of the pile group, which shows that with the development of soil’s rheology, the internal force gap between corner piles and central piles gradually shrinks and tends to be stable.

Key words: fractional merchant model, viscoelasticity, saturated soils, laterally loaded pile groups, interaction analysis