Soil Behavior under Vibratory Driving

Vibratory driving of piles and soil densification raise several engineering issues including the long-term bearing capacity of the installed pile, its vibratory penetration resistance, the performance of vibrators, the degradation and liquefaction of the soil around the vibrated profile, and vibratory nuisance to the environment. An argument is made that those issues will be adequately tackled once combined into a comprehensive framework of analysis where proper understanding of soil behavior is the key. The present paper reviews our current engineering ability to assess vibro-drivability, i.e. predicting the vibratory penetration log of a given pile into a given soil profile using a given vibrator. Testing undertaken to provide insight into the pile-soil-vibrator interaction and its modelling is then emphasized. Several available methods to establish the vibratory performance of a pile from its vibratory capacity are discussed. A rational procedure to model the dynamic nonlinear soil structure interaction during pile vibratory driving is discussed in more detail. Degradation of the skin friction upon cyclic shear stress is evaluated by applying elements of earthquake engineering practice used to assess liquefaction potential. The present ability to assess the vibratory capacity of a pile from the monitoring of its vibratory performance is critically reviewed. Finally, suggestions for further research, design and practice are provided.