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Proceedings Paper

Impulse-response testing to evaluate the degree of alkali-aggregate reaction in concrete drilled-shaft foundations for electricity transmission towers
Author(s): Allen Davis; James Kennedy
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Paper Abstract

Alkali-aggregate reaction (AAR) has affected the concrete in drilled shafts (cast in place piles) beneath electricity transmission towers along a 42-mile (67 km) section of transmission line in Southern California. In order to prioritize the maintenance program for these shafts, a nondestructive test methodology was sought to quantify the severity of the AAR with depth in each shaft. Shaft diameters of 19, 30, 36, 42, and 54 inches (475, 760, 910, 1067 and 1660 mm) were present, with shaft lengths between 10 and 30 feet (3 and 6 m). Over the last thirty years, impulse-response (I-R) testing has been successfully used to evaluate the integrity of drilled shafts, and computer simulation programs have also been developed for matching I-R test responses with theoretical shaft shapes and concrete quality. A program to test as many shafts as could be accessed in the difficult, mountainous terrain along this transmission line included mobilization of equipment and testing personnel by helicopter. Two hundred ten shafts were tested along the line in five days. Matching of test response mobility-frequency plots in computer simulation was achieved by varying the simulated concrete modulus and density, as well as the shaft cross section area. Up to three grades of concrete quality were identified in each shaft, representing the decreasing degree of AAR with depth. The tested shafts were then rated for increasing AAR severity, in order to select shafts for repair or replacement.

Paper Details

Date Published: 15 March 1998
PDF: 8 pages
Proc. SPIE 3398, Nondestructive Evaluation of Utilities and Pipelines II, (15 March 1998); doi: 10.1117/12.302523
Show Author Affiliations
Allen Davis, Construction Technology Labs., Inc. (United States)
James Kennedy, Southern California Edison Co. (United States)

Published in SPIE Proceedings Vol. 3398:
Nondestructive Evaluation of Utilities and Pipelines II
Walter G. Reuter, Editor(s)

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