Studying of the dynamic behavior of pile cushioning materials in pile driving

The dynamic behavior of cushioning materials such as hardwood, particle board, pinewood, asbestos-rubber board, and disk springs are fully characterized by different experimental methods. These include static elastic modulus by static loading, dynamic elastic modulus by natural frequency using the cantilever method, dynamic stress-strain curve method, dynamic recovery coefficient by normal impact between a spherule and a plate, and the pile-driving test in a sand pit. The experimental results show that the relationships between dynamic stresses and strains of the pinewood and asbestos-rubber board are quite different compared with the static ones and subsequently result in greater elastic modulus and recovery coefficients. In comparison to the minor effect on reducing pile-driving stresses of the pile body for pinewood, disk springs are a preferred cushioning material because of their stable dynamic properties that can greatly reduce the driving compressive stresses of the pile body. Copyright © 2006 by ASTM International.