Evaluation of excess pore pressure and liquefaction for rocking wind turbine foundations

Restrictions on uplifts of shallow foundations have been modified for bridge and building foundations to enable more efficient and sustainable performance-based design. This new philosophy of designing foundations against strong earthquake shaking is also being considered for wind turbine foundations in recent years. In order to allow foundation uplifts in saturated sand, the effects of induced cyclic strains on liquefaction susceptibility should be addressed. In this paper, an efficient method for computation of excess pore pressure accumulation and dissipation in saturated sand is incorporated into finite element modeling of a rocking foundation. The developed model is validated against experimental data from centrifuge tests of shallow foundation resting on saturated sand. Subsequently, the validated methodology is applied to finite element simulation of wind turbine foundations. The results demonstrated that a small uplift region can be tolerated to develop under operational conditions of a wind turbine foundation in saturated sand without occurrence of liquefaction. A reconsideration and easing of the uplift restrictions can lead to economical designs for new foundations of wind turbines and re-purposing of existing foundations for larger wind turbines.