Civil Engineering Association

Recommended Practice for Evaluation of Metal-Tensioned Systems in Geotechnical Applications

This report documents and presents results of a study on evaluating remaining service life of metal-tensioned systems, including rock bolts, tiebacks, and soil nails. A recommended practice is proposed describing procedures to evaluate the condition and remaining useful life of in-place, metal-tensioned systems and to estimate the design life of new installations. The recommended practice considers key factors such as materials used in the tensioned systems; corrosion; anchorage methods; soil and rock conditions; environmental effects; construction techniques; and long-term, cost-effective measuring techniques. Nondestructive testing (NDT) techniques--including measurement of half-cell potential and polarization current, impact echo testing, and ultrasonic probing--are used for condition assessment of metal-tensioned systems. NDT techniques are included in the recommended practice to supplement destructive tests, which provide the most reliable information needed for recommending future actions. Application of the recommended practice is demonstrated through field investigation of an inventory of existing metal-tensioned systems representing a range of types, subsurface conditions, and ages. Data from the field studies serve to validate the measurement methods, the corrosion assessment model, and the model for estimating the remaining useful service life described in the recommended practice.