Experimental study on friction fatigue of vibratory driven piles by in situ model tests

Abstract

Friction fatigue is an important factor to consider for pile drivability during the installation of piles. Only a few studies have focused on the friction fatigue of vibratory driven piles. However, the friction fatigue of jack-in piles has been investigated extensively. Therefore, this study focuses on the friction fatigue of vibratory driven piles. A total of six in situ vibratory pile driving tests were conducted with different frequencies and different vibratory forces. Both the acceleration at the pile head and the axial strain of the pile were monitored during vibratory driving. The shaft friction, τSij, was analyzed at each section of the pile during vibratory driving, and the decrease in friction (i.e., friction fatigue) was observed. The concept of accumulated shear work, W, was introduced during vibratory driving, and a unified relationship was established between the decrease in shaft friction normalized by the cone tip resistance, τSij/qc, and W. From a practical viewpoint, this concept will be helpful for the construction management of vibratory pile driving and for determining the vibratory hammer specifications.