Evaluation of the base condition of drilled shafts by the impact-echo method

Abstract

Numerical and experimental model studies were carried out to evaluate the base condition of drilled shafts. Base conditions such as free, fixed, rock-socketed, and soft-bottom were considered. To simulate the base conditions, mock-up shaft models made of cement mortar were used. The impact-echo method was applied to evaluate each base condition. Finally, field tests were performed for the rock-socketed shafts. It is found that the rock-socketed condition and socketed length can be evaluated. The soft bottom condition can be identified, only when the side contact between shaft and surrounding rock is poor, whereas it cannot be identified when the side contact is good.