Estimating the flaw size in drilled shafts using an impulse response method

Flaws could occur in drilled shafts due to improper quality control, poor workmanship, and unexpected construction mistakes, and thus seriously decrease the loading capacity. This paper proposes a flaw size estimation formula for use in the impulse response test of drilled shafts. Numerical models were built to develop the estimation formula. The experimental cases also validate the estimation. The flaw depth ratio and stiffness ratio are two key parameters to accomplish the estimation. With the evaluation results of the formula, one can know the possible minimum flaw size in the drilled shaft and further remedial measures can be taken immediately. Furthermore, the detectable shaft slenderness ratio is shown to vary from 10 to 30, depending on the stiffness ratio.