Experimental investigation of the impact of the installation method on the lateral behavior of piles

In response to the latest IPCC reports on the climate emergency and the explosion of the energy markets, European countries are increasingly switching to renewable energy sources such as solar panels and wind turbines to provide their electricity. These energy sources are inexhaustible, more sustainable and contribute to the development of some world regions but their main drawback is that they are intermittent. In addition, the European Union has a goal of achieving carbon neutrality by 2050, which means that in less than 30 years, the entire energy system must be revised to include more sustainable energy sources. Offshore wind turbines are a great opportunity to meet this challenge and reduce the environmental impact of energy production, although they are expensive and take time to repair. In order to support the wind turbine at sea, foundations embedded in the seabed or floating are required. Currently, wind turbines are mostly installed in shallow waters up to 40-50 m deep and are mainly founded on monopile foundations. Two main installation techniques are considered nowadays : impact driving or vibratory driving. Impact driving consists of hitting the pile top with a hammer, often hydraulic, to drive it into the seabed. This technique is widely used because it allows for a high bearing capacity and its application to a variety of soil conditions. However, the vibrations induced by impact driving cause significant disturbance to marine life or buildings near wind farms. To overcome the negative environmental impacts, the economic costs and the slowness of impact driving, vibratory driving was developed. This technique takes advantage of the fact that the shear strength decreases under cyclic loading by a vibrator and makes it easier to drive the pile. However, the long-term strength of the vibrated pile is not well known at present and is still the subject of research and experimentation in full-scale and laboratory settings. In this context, this thesis investigates the influence of the embedded length, the drop height of the hammer and the relative density of the dry sand on the pile’s lateral behaviour during the driving process with the goal of being able to compare these results later on with those obtained during vibratory driving.