Nondestructive Evaluation of Existing Deep Foundations

Abstract

Nondestructive testing (NDT) for the evaluation of deep foundations has been practiced for more than a quarter of a century, usually on new construction projects. It is not always realized that the performance evaluation of older, deep foundations under existing structures can be enhanced by nondestructive testing. The NDT techniques currently available for this objective are described and critically reviewed in this paper. Case histories illustrating the use of different methods to inspect existing piles, drilled shafts, and caissons are presented. Most of these NDT methods are applied in Europe and East Asia, and the present limited use of small-strain nondestructive testing in the North American deep foundation industry is discussed. It is concluded that the methods described in this paper could be usefully employed more often; their limited use is mainly a result of unfamiliarity with the tests and a lack of awareness of their potential by the general engineering community.