Non-overlapping friction element for soil-structure interaction and its application

To solve the problem of overlapping of Goodman element, this paper proposes a non-overlapping friction element, which is integrated into a finite element model of soil-structure interaction and programed for calculate. It utilizes the soil mass as a solid elasto-plastic element and the retaining pile of slopes or foundation pits as beam elements. The Goodman four-node, eight-degree-of-freedom element at the interface between soil and beam is simplified to a four-node, six-degree-of-freedom non-overlapping friction element. That is uniting the two adjacent normal degrees of freedom of the Goodman element into one under compression condition. The non-overlapping friction element allows for tangential sliding without normal overlapping or separation. The corresponding finite element algorithm is established by constructing the element stiffness matrix of the non-overlapping friction element and assembling it in the global stiffness matrix, and a computational program is developed. The cases study indicates that when the normal stiffness of the Goodman element is sufficiently large, its computational results are essentially consistent with those of the embedded frictionless element, with the latter being the limiting solution as the normal stiffness of the Goodman element continuously increases. The non-overlapping friction element algorithmically avoids the overlapping caused by the normal stiffness, and provides a rigorous solution for soil-structure interaction.