Accumulative displacement of long-term cyclic laterally loaded monopiles with large diameter sand

The accumulative displacement of offshore wind power under long-term cyclic lateral loads from wind and wave loads attracts a lot of attention, for it may lead to the malfunction of a wind turbine. Considering the cyclic loading characteristics of sandy soil around piles, the lateral cyclic response of monopile for offshore wind power is investigated. The R-O loading curve and modified Masing rule are used to construct loading and unloading stress-strain curves of sand. Based on the explicit equation for cyclic accumulative axial strain of sand, a cyclic evolution model for secant stiffness of sand is derived, and it is applied in the FE analysis. By comparing with the published centrifuge test results of a laterally loaded monopile in sand, the rationality of the evolution model is verified. A parametric analysis considering different embedment lengths of the pile is also undertaken. It is believed that the FE analysis with the evolution model for secant stiffness of sand can rationally simulate the development of the accumulative rotation of a horizontal cyclic loaded monopile, which provides theoretical support for the design of the cyclic response of wind turbines.