Installation Effect Of The Penetration Of Large-diameter Monopiles For Wind Turbine By Using The High-Frequency Vibratory Hammers

With the government paying attention to the exploitation of the wind energy,a growing numbers of wind turbines are constructed near the coast.The large-diameter monopiles,which have the advantages of being economical,effective and extensively applicable,is widely used in the practical engineering.The monopiles are usually installed with the help of the high-frequency vibratory hammmers,so the driving of the large-diameter monopiles is influenced by the cyclic loading induced by the vibratory hammers,which differentiates the penetration process from the penetration by using the jacking and hammering method.So far,the investigations on the high-frequency vibratory driving of the large-diameter monopiles are not completed,especially the study on the installation effect and soil plugging effect during the installation process is relatively insufficient.This thesis aims to investigate the installation and soil plugging effect during the high-frequency vibratory driving process.The major works in this thesis are listed below.By using the Coupled Eulerian-Lagrange(CEL)method,a numerical modeling of high-frequency vibratory driving of the large-diameter monopiles into sands and clays is established.The variation of the inner and outside friction.pressure factors and soil plugging effect during the high-frequency vibratory penetration is revealed and analyzed.The stress distribution in the pile toe during the vibratory penetration into sands is investigated,and the parametric study of soils and vibratory hammers on the soil plugging effect.The installation effect of the high-frequency vibratory penetration of the large-diameter monopiles into two different soils is compared and analyzed.The soils displacement and stress during the vibratory driving process are plotted,and the influence of the apertures on the installation effect is studied.Therefore,the variation of penetration speed is also investigated.According to numerical simulation result,the plastic regions around on pile end is close to the assumption of the Meyerhof deep foundation bearing capacity,so the Meyerhof deep foundation bearing capacity formula is introduced in the discrimination formula of soil plugging effect,which is based on the pseudo-static method,and credibility of this formula is proven by the three laboratory tests.