Cyclic response of wind turbine on piles in unsaturated sand

The performance of the onshore wind turbine resting on pile foundations, installed in partially saturated soils, has not received adequate attention from geotechnical researchers to date. Therefore, the objective of this paper is to highlight the influence of different controlling factors to this interaction including: geometrical arrangement of piles, types of soils, degree of saturation and the strain range associated with lateral cyclic loading. An experimental study has been carried out using pile models founded into medium dense sandy soils. Three different pile arrangements (single, 31 and 33 grouped piles) of 10, 20 and 30 slenderness ratio were used in this research. Two-way lateral cyclic loading displacements of several frequencies were applied on pile head. The experimental set-up is discussed in detail, and the results are presented in the form of normalised cyclic load-displacement curves as well as normalised bending moment charts against the number of cycles. Furthermore, secant modulus of subgrade reaction, cyclic p-y curves and the potential of soil liquefaction adjacent to the pile shaft were estimated. The results provide an insight into the key parameters that are controlling the performance of wind turbines founded pile foundations subjected only to lateral cyclic loading conditions.