Location

Arlington, Virginia

Session Start Date

8-11-2008

Session End Date

8-16-2008

Abstract

The importance of vibration problems induced by pile driving is addressed and guidelines for establishing limiting vibration levels with respect to buildings with different foundation conditions are presented. Basic concepts of pile dynamics and stress-wave measurements, which were developed for the determination of driving resistance and bearing capacity of impact-driven piles, provide important information about ground vibration induced by pile penetration. Dynamic hammer properties and geometry as well as the driving process are important for ground vibration emission from the pile. It is shown that the energy-based, empirical approach, which is still widely used by practicing engineers, is too crude for reliable analysis of ground vibrations and can even be misleading. The main limitations of the energy approach are the assumption that driving energy governs ground vibrations, the omission of geotechnical conditions and soil resistance, and the uncertainty with regard to input values. Three types of ground waves are considered when analyzing pile driving: spherical waves emitted from the pile toe, cylindrical waves propagating laterally from the pile shaft, and surface waves, which are generated by wave refraction at the ground surface at a critical distance from the pile. These three wave types depend on the velocity-dependent soil resistance at the pile-soil interface. The most important factor for analyzing ground vibrations is the impedance of each system component, i.e., the pile hammer, the pile, and the soil along the shaft and at the pile toe. Guidance based on geotechnical conditions is given as to the selection of appropriate impedance values for different soil types. A theoretical concept is presented, based on a simplified model that considers the strain-softening effect on wave velocity in the soil, making it possible to calculate the attenuation of spherical and surface waves and of cylindrical waves generated at the pile toe and the pile shaft, respectively. The concept is applied to define k-values, which have been used in empirically developed models and correlated to type of wave and soil properties. An important aspect of the proposed prediction model is the introduction of vibration transmission efficacy, a factor which limits the amount of vibration force that can be transmitted along the pile-soil interface (toe and shaft). Results from detailed vibration measurements are compared to values calculated from the proposed model. The agreement is very good and suggests that the new model captures the important aspects of ground vibration during penetration of the pile into different soil layers. Finally, based on the presented model, factors influencing the emission of ground vibrations during impact pile driving are discussed.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Sixth Conference

Publisher

Missouri University of Science and Technology

Publication Date

8-11-2008

Document Version

Final Version

Rights

© 2008 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

Share

 
COinS
 
Aug 11th, 12:00 AM Aug 16th, 12:00 AM

Ground Vibrations Induced by Impact Pile Driving

Arlington, Virginia

The importance of vibration problems induced by pile driving is addressed and guidelines for establishing limiting vibration levels with respect to buildings with different foundation conditions are presented. Basic concepts of pile dynamics and stress-wave measurements, which were developed for the determination of driving resistance and bearing capacity of impact-driven piles, provide important information about ground vibration induced by pile penetration. Dynamic hammer properties and geometry as well as the driving process are important for ground vibration emission from the pile. It is shown that the energy-based, empirical approach, which is still widely used by practicing engineers, is too crude for reliable analysis of ground vibrations and can even be misleading. The main limitations of the energy approach are the assumption that driving energy governs ground vibrations, the omission of geotechnical conditions and soil resistance, and the uncertainty with regard to input values. Three types of ground waves are considered when analyzing pile driving: spherical waves emitted from the pile toe, cylindrical waves propagating laterally from the pile shaft, and surface waves, which are generated by wave refraction at the ground surface at a critical distance from the pile. These three wave types depend on the velocity-dependent soil resistance at the pile-soil interface. The most important factor for analyzing ground vibrations is the impedance of each system component, i.e., the pile hammer, the pile, and the soil along the shaft and at the pile toe. Guidance based on geotechnical conditions is given as to the selection of appropriate impedance values for different soil types. A theoretical concept is presented, based on a simplified model that considers the strain-softening effect on wave velocity in the soil, making it possible to calculate the attenuation of spherical and surface waves and of cylindrical waves generated at the pile toe and the pile shaft, respectively. The concept is applied to define k-values, which have been used in empirically developed models and correlated to type of wave and soil properties. An important aspect of the proposed prediction model is the introduction of vibration transmission efficacy, a factor which limits the amount of vibration force that can be transmitted along the pile-soil interface (toe and shaft). Results from detailed vibration measurements are compared to values calculated from the proposed model. The agreement is very good and suggests that the new model captures the important aspects of ground vibration during penetration of the pile into different soil layers. Finally, based on the presented model, factors influencing the emission of ground vibrations during impact pile driving are discussed.