Lateral dynamics of a monopile partially embedded in layered saturated soil with radial disturbance

A bidirectional transfer matrix method is presented to investigate the impedances of a laterally loaded monopile partially embedded in layered saturated soil with radial disturbance. To characterize the radial variation of soil properties induced by construction excitations or cyclic lateral excitations, the radial transfer matrix of the saturated soil is developed to determine the horizontal resistance of soil to the pile shaft based on Biot's theory. Lateral, rocking and lateral-rocking coupled impedances at the head of the monopile are obtained by solving the differential equations for transverse vibration of the pile shaft based on the Timoshenko beam theory, combined with an axial transfer matrix to treat the layered property of soil along the partially embedded monopile. The proposed model is validated by comparing it with some existing results. The theoretical rigour and broad engineering applicability of the present model are highlighted by a series of parametric analyses for the influences of soil and pile properties on the impedances of the laterally loaded monopile.