Effects of liquefied soil properties on soil-monopile-wind turbine structure interaction

The main goal of the 2030 sustainable development plan is to develop access to renewable, sustainable, reliable and cost-effective energy. One of the renewable energy sources is wind energy, which is produced using wind turbines. These turbines are mainly used in coastal or offshore areas that are seismic and liquefied. The development of these turbines in areas with high seismic potential and liquefied soils has necessitated the use of piles and other deep foundations. In this paper, the effect of liquefied soil layer characteristics on the soil-mono pile interaction under the effects of far and near field earthquake records has been investigated. Dynamic nonlinear time history analyses were performed by considering four types of liquefied sand with a thickness of 5 m, under 2 kW turbine load and the effect of 14 earthquake records. Nonlinear analyses are performed in OpenSees software by considering the appropriate behavioral model for soil layers and the interaction between the pile and the soil. The results showed that in earthquakes with a PGA less than 0.4 g and in sandy soils with a density of more than 70% liquefaction does not occur. The highest displacement is related to the pile located in T1 soil, which has the lowest internal friction angle (ɸ = 30) and the lowest soil compaction percentage. With the occurrence of liquefaction in the middle layer, the support level of the monopile is transferred from ground to the end of the liquefiable layer. Based on the results the values of maximum pore pressure, flexural moment and shear force of the soil under near and far-field records decrease with increasing soil density that is more evident for far-field earthquakes.