RESPONSE OF A FRESHLY PLACED FULL SCALE CONCRETE
DRILLED SHAFT TO VIBRATIONS INDUCED BY ADJACENT
OUR WORLD IN CONCRETE & STRUCTURES - 2012
D.V. Reddy, C.S. Gonzalez-Mier and K. Sobhan
Construction, Vibration, Early-Age, Concrete
A number of studies have been conducted in an effort to understand
wave attenuation and sound response during installation of deep foundations.
This research stems from the need to better understand the effect of vibration on
freshly placed and maturing concrete within 24-hours after initial placement.
Construction activities create vibratory inducing forces, which unaccounted for or
unmitigated, have detrimental effects to existing and newly in-place structures. The
differences between common construction vibrations, and those produced during
deep foundation construction, are the amplitudes and durations. The study focuses
on effects during the installation of deep foundations through vibratory methods and the age effect of the vibrations on freshly placed concrete. The installation followed the Florida Department of Transportation (FDOT) guidelines. During the drilled shaft casing installation, vibration is transmitted from the source of installation to the surrounding soil causing ground motion affecting the adjacent structures. The intensity of the ground motion and the severity of the induced vibration depend on factors such as soil type, form of amplitude-time history of the vibration, polarity of certain type of waves and configuration of the adjacent structures. The field investigation monitored peak particle velocities during installation and their effect on freshly placed concrete. The principal findings from the field study were: (1) vibrations with peak particle velocities of up to 2.5 in/sec do not cause damage to the fresh concrete at distances of two times the shaft diameter and beyond, and (2) in general, a spacing of three times the shaft diameter is a safe specification for ensuring that shaft vibration does not damage the concrete.