Impact-Echo Response of Concrete Shafts
Numerical and experimental studies of the transient response of concrete shafts subjected to elastic impact were carried out using the finite element method and the impact-echo testing technique. Two- and three-dimensional finite element studies of concrete shafts were performed for: (a) solid shafts; (b) shafts containing cracks, voids, layers of low-quality concrete, and changes in cross section, such as bulges and necks; and (c) shafts in soil. These studies were carried out to gain an improved understanding of the impact response of concrete shafts containing flaws, problems for which there are currently no analytical solutions. It was also the intent of the numerical studies to determine whether information in addition to that obtained with existing nondestructive testing techniques could be obtained during impact testing of concrete shafts. Laboratory studies of solid concrete shafts were carried out to verify the finite element models. Subsequently, experimental studies were carried out on concrete shafts embedded in soil. These shafts contained flaws at known locations. The results of these studies show that additional information about the integrity of drilled shafts and piles can be obtained using impact techniques. The numerical studies also show that the finite element method is a powerful tool for studying the impact response of concrete foundation elements.