PARSAn Overseas Pvt. Ltd, New Delhi
Online published on 13 January, 2020.
As large dams age, it becomes increasingly important to determine the condition of their material and to track changes in this condition over time. Inspections of concrete, masonry and earthen dams, dikes and spillways often require testing to evaluate for leakage paths, soil settlement/voiding, or weakened deteriorated concrete/masonry.
NDT uses geophysical testing methods (ground penetrating radar, 2d/3d electrical resistivity imaging, streaming potential) to identify potential leakage paths under earthen dams, dikes and concrete spillways. Sonic/ultrasonic impact echo, cross-face sonic tomography and GPR non-destructive testing methods are used to identify voided areas under spillways. Sonic/ultrasonic pulse velocity, cross-face sonic tomography, MASW and impact-echo measurements are also used to determine the condition and integrity of dam and spillway concrete.
Although long recognized that dams need periodic inspection and monitoring, it has only been recently recognized that geophysical surveys can supplement the results of standard inspection and monitoring techniques. Geophysical surveys have been performed on a number of dams around the world, including India, and have yielded extremely useful insight into dam conditions. The choice of right tool, timing of such investigation and deliverables expected are, however, not very well defined at the moment.
Present paper defines available ndT tools and techniques applicable to earthen, masonry and concrete dams, presents guidelines for selection of appropriate method and establishes the investigation methodology.
