Development of Innovative Foundation Configuration for Tall Wind Turbines Inspired by Tree Root System

Abstract

This study presents a simplified analytical design and numerical modeling of the pile group foundation for a wind turbine tower on multilayered soil. The pile group foundation obtained from the analytical design is modified to study the possibility of developing an innovative foundation configuration through biomimicry of the tree root system. The initial dimensions of the pile group foundation were obtained from the analytical geotechnical design, which resulted in 40 closed-end steel pipe piles of length 30 m arranged along the circumferences with radii 5.3 and 6.7 m. The pile cap is considered to have a radius of 7.5 m and a thickness of 1.2 m. These dimensions were used to develop a three-dimensional numerical model of the pile group foundation in GROUP software. Inspired by the load-carrying mechanism of the natural foundation, i.e., tree root system, the initial model was modified by altering the inclination of the outer piles, which resulted in an additional ten models. The results from GROUP indicated that the differential settlement and rotation are the lowest for the model with outer piles inclined at an alternate 60° and 45° with the horizontal plane. Further, the pile configuration was modified by arranging the same number of piles along three circumferences keeping the length of the pile constant. This configuration was modified by changing the inclination of middle and outermost piles, which resulted in additional 14 models. These models were analyzed in GROUP, and the results showed that the lowest differential settlement and rotation are observed in the model with piles inclined at an angle of 90°/90°/60° (innermost/middle/outermost pile) and 90°/90°/45°. Moreover, the stress, axial force, shear force, and bending moment were obtained from GROUP for each configuration, which can be used to ensure the structural safety of the foundation.