Fundamentals of the vibratory driving of piles and sheet piles

Abstract

Abstract Vibratory driving is a common method for installing or extracting piles and sheet piles as well as for deep vibratory compaction. The most important parameters are vibration frequency, vibration amplitude and eccentric moment. These parameters govern vibratory driving and, in particular, the soil resistance at the toe and along the shaft of a pile. Pile driving causes oscillating horizontal ground vibrations in coarse‐grained soils. It can be shown that these horizontal vibrations reduce the shaft resistance during driving. The process results in a permanent increase in the horizontal effective stress, which causes arching around the vibrated pile. The increase in horizontal effective stress is also important for deep vibratory compaction. The resonance frequency of the vibrator‐pile‐soil system significantly affects pile penetration and the emission of ground vibrations. At resonance, the vertical vibration velocity in the soil reaches a maximum and pile penetration becomes very slow, whereas beyond resonance, the vibration velocity decreases and the pile penetration speed is high. Field monitoring of the vibratory driving process can be used to optimize vibratory pile driving, as examples have shown. A new concept is proposed in which the driveability can be determined from a correlation between penetration resistance measurements (blows/depth) and penetration speed. The validity of the concept is demonstrated by a case history and project references.