Pile damage prevention and assessment using dynamic monitoring and the beta method

Driven piles are subjected to high stresses during installation. It is, therefore, important not to exceed acceptable stresses along the pile shaft and at the toe to prevent damage. Dynamic monitoring has been used for decades to evaluate not only the installation stresses, but also to check test piles for signs of structural damage. The Beta Method (β-Method) for evaluation of the location and extent of a potential damage was developed more than 30 years ago and has proven effective as a QC and QA tool. As an aid in the process of pile rejection or acceptance, the β-method also offers a rating scale that translates the automatically determined β-number into a helpful pile integrity assessment tool. The reliability of this algorithm has been proven by numerous extracted piles. However, one limitation of the β-method concerned detection of damage near the pile toe where high toe resistance effects and/or stress wave reflections reduce the effectiveness of the traditional β-method. In the past, therefore, near-toe damage was determined by the testing engineer, not only by visual inspection of the dynamic monitoring data, but also by reviewing the pile toe compressive stresses throughout the monitored driving history and the strength and stiffness of the soil response from the pile toe. This approach has now been automated and subjected to tests on existing data. After a review of the existing methods of pile stress and damage calculations, the paper presents the new method, illustrating its effectiveness by examples from measurements on both concrete and steel piles. © 2014 American Society of Civil Engineers.