Semiempirical Model of Vibration-Induced Ground Deformations due to Impact Pile Driving

A semiempirical method to determine ground deformations and vibrations induced by impact pile driving in sandy soil conditions is presented in this study. Field data during installation of precast prestressed concrete piles with impact hammers were obtained in terms of ground deformations and peak particle velocities. Semiempirical equations are proposed using a combination of field measurements and numerical analyses to consider the following triggering factors for the ground response due to impact pile driving operations: (1) rated energy of the hammer, (2) scaled distance from the pile, (3) pre-drilling depth, and (4) relative void ratio, which is closely related to the relative density. The numerical component of this framework was developed adopting a continuous pile driving modeling approach coupled with the Updated Lagrangian approach to deal with large deformations and an advanced constitutive soil model (i.e., hypoplasticity for sands enhanced with the intergranular strain concept) capable of reproducing changes in soil void ratios during pile installation. The model parameters were adopted by computationally matching published nonlinear shear modulus degradation curves of the granular layers. A highly disturbed zone close to the pile was computed arising from pile driving-induced soil liquefaction causing large variations in computed void ratios. It was concluded that even if vibration levels are below typical vibration limits defined by regulatory agencies, large levels of ground deformations can still occur. The proposed method is validated in terms of ground vibrations and deformations induced by impact pile driving using field measurements, published vibration attenuation curves, and vibration-induced ground surface settlement prediction methods.