Crosshole seismic tomography across a masonry dam

Joe Wong

doi:10.1117/12.209404

12 May 1995 Crosshole seismic tomography across a masonry dam

Joe Wong

Proceedings Volume 2457, Nondestructive Evaluation of Aging Structures and Dams; (1995) https://doi.org/10.1117/12.209404
Event: Nondestructive Evaluation of Aging Infrastructure, 1995, Oakland, CA, United States

Abstract

An intensive crosshole seismic survey was done across a 700-foot-long stone-masonry dam. It involved measurements on six connected panels each approximately 100 feet in width extending completely across the dam from abutment to abutment. The objective was to provide tomographic images of P-wave velocity and dynamic elastic moduli of the dam and foundation materials along the axis of the dam. Field seismograms were recorded with an airgun source and hydrophone detectors. Data analysis included interactive time-picking, plotting of common source gathers, and tomographic imaging using an iterative back-propagation technique. Color-coded tomograms of velocity and dynamic Young's modulus were produced and correlated with geological and geophysical data measured on drill core samples. Low values of velocity and dynamic elastic modulus correlated with low RQD and high fracture frequency. The tomograms showed significant variations of mechanical properties in the stone masonry dam and its foundation. The colored tomograms were useful in highlighting zones of weak rock possibly requiring remedial action. They also assisted engineering evaluation of the dam by providing a detailed two-dimensional distribution of mechanical properties which can be used as ground truth data for numerical modeling of stress-strain fields.

Citation Download Citation

Joe Wong "Crosshole seismic tomography across a masonry dam", Proc. SPIE 2457, Nondestructive Evaluation of Aging Structures and Dams, (12 May 1995); https://doi.org/10.1117/12.209404

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