Defect and Length Predictions by NDT Methods for Nine Bored Piles

Nine bored piles were built at the National Geotechnical Experimentation Sites at Texas A&M University: five at the sand site and four at the clay site. The piles had a nominal diameter of 0.915 m and varied in length from 10.7 m to 24.1 m. Various defects were intentionally placed in the piles including necking, bulging, soft bottom, tremie displacement, mud cake, and inclusion. Five companies were invited to make class A predictions of the length of the piles and of the defects size and location. They used small strain dynamic methods including sonic echo, impulse response, impedance logging, and sonic logging. The results are an indication of how reliable these methods are for predicting length and defects.