Analysis of a wind turbine foundation on stiff clay with analytical and 3D finite element methods

Yaşar, Baki Eren
Optimum design of onshore wind turbine foundations have been a topic of interest in geotechnical engineering in recent decades. However, the literature is lacking a systematic methodology for the design of onshore wind turbine foundations with three-dimensional finite element method (3D FEM) and a practical study evaluating the factors affecting the foundation design. The goals of this study are (i) to present a comprehensive design procedure by summarizing the literature, (ii) to investigate the key issues for the design of onshore wind turbine foundations using 3D FEM and (iii) to highlight the important factors for ensuring both safe and economical design. For these purposes, a wind turbine with 1.5 MW capacity on stiff clay was taken as a case study and the analyses of the foundation (in terms of bearing capacity, overturning, sliding, rocking stiffness, elastic settlement and rotation) were conducted using analytical method, probabilistic method using Monte Carlo simulation, and 3D FEM. In conclusion, to calculate the settlement and rotation of wind turbine foundations accurately, using 3D finite element analysis was recommended instead of analytical method. Furthermore, the variation in foundation diameter and soil properties, i.e., different coefficient of variation (COV) levels, on satisfactory performance was evaluated. It was noted that the increase of COV level causes an increase in the probability of unsatisfactory performance of the foundation. This study demonstrates a foundation design methodology for practicing engineers and will be useful to reach robust, safe and economical foundation design for wind turbines considering the variability in soil properties.