Effect of Construction Induced Vibrations on Green Concrete in Drilled Shafts

This study was concerned with vibrations induced during drilled shaft construction on green concrete in adjacent drilled shafts. To characterize the types of vibrations, a full-scale field test was conducted using a 0.9-m (3-ft)-diameter steel casing vibrated at a peak particle velocity (ppv) of 250 mm/s (10 in./s) to various depths in a sandy soil layer. In addition to the steel casing, the peak particle velocities were recorded at different distances and depths from the vibration source. Empirical relationships from measurements were developed to predict the velocity values on the surface and in the ground along the penetration depth of the steel casing. Laboratory tests were conducted on two groups of green concrete samples to determine the effect of ppv and curing time on concrete properties. These tests showed a 10% reduction in the 28-day compressive strength for samples subjected to continuous vibration at ppv of 50 mm/s (2 in./s) for a duration ranging from the initial to the final setting time. On the other hand, when samples were continuously vibrated until the final setting time, the 28-day compressive strength of the concrete increased by 10%. If vibrations with ppv of 50 mm/s are unavoidable, curing caissons shall be kept at a distance of more than two shaft diameters from the source of vibration.