Proceedings of the Institution of Civil Engineers http://dx.doi.org/10.1680/geng.11.00094 Paper 1100094 Received 09/10/2011 Accepted 04/04/2012 Keywords: dynamics/mathematical modelling/piles & piling
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Numerical study of ground vibration due to impact pile driving 1 j Ali Khoubani MSc 2 j Mohammad Mehdi Ahmadi PhD
Senior Geotechnical Engineer, Department of Civil Engineering, Sharif University of Technology, Tehran, Iran
Associate Professor, Department of Civil Engineering, Sharif University of Technology, Tehran, Iran
Ground vibration due to pile driving is a long-lasting concern associated with the foundation construction industry. It is of great importance to estimate the level of vibration prior to the beginning of pile driving, to avoid structural damage, or disturbance of building occupants. In this study, an axisymmetric ﬁnite-element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code Abaqus, to simulate full penetration of the pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been veriﬁed by comparing the computed particle velocities with those measured in the ﬁeld. The results indicate that the peak particle velocity at the ground surface does not occur when the pile toe is on the ground surface; as the pile penetrates into the ground, the particle velocity reaches a maximum value at a critical depth of penetration. Some sensitivity analyses have been performed to evaluate the effect of soil, pile and hammer properties on the level of vibrations. The results show that increase in pile diameter, hammer impact force, soil–pile friction and reduction in soil elastic modulus can increase the peak particle velocity.
D d E e L Lmin p r VP VR VS Æ â ˜t ¨ ì í r ô ôcrit ö pile diameter depth of penetration of pile elastic modulus deviatoric eccentricity distance between vibration source and reﬂective origin of Rayleigh waves at ground surface smallest element dimension in mesh pressure radial distance from pile centreline velocity of compression wave velocity of the Rayleigh wave velocity of shear wave Rayleigh mass proportional damping Rayleigh stiffness proportional damping stable time increment angle of deviatoric stress plane axes coefﬁcient of friction Poisson’s ratio density shear stress critical shear stress soil friction angle
î îmax ømax øn ø1
damping ratio damping ratio in mode with highest frequency highest frequency of model natural frequency associated with 95% of modal mass of model ﬁrst natural frequency of model
Pile driving is an age-tested method of constructing foundations where adequate ground support is not directly available. However, it is also a source of negative environmental effects. Noise and air pollution are the most commonly expressed concerns, but these are also relatively easily alleviated. By contrast, vibrations originating from impact pile driving are both difﬁcult to determine beforehand and costly to mitigate, while potentially having serious adverse effects on adjacent structures and their foundations, as well as on vibration-sensitive installations and occupants of buildings (Massarsch and Fellenius, 2008). During recent decades, several investigations have been performed to determine the characteristics of pile driving vibrations. One common method of handling vibrations is to perform ﬁeld measurements in terms of the peak particle velocity (PPV) during 1
Numerical study of ground vibration due to impact pile driving Khoubani and Ahmadi
pile driving, to determine the soil attenuation properties. The PPV is the maximum velocity that a soil particle experiences during the driving of a pile from the ground surface to the desired depth. The...