Estimating Spatial Variations in Bedrock Depth and Weathering Degree in Decomposed Granite from Surface Waves
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 143, Issue 7
Abstract
In Singapore, sudden changes of bedrock depth and highly variable weathering degrees in residual soils are commonly observed. This study employed the dispersive characteristics of Rayleigh-type surface waves from combined active-source and passive-source surface-wave techniques to (1) generate S-wave velocity () profiles of residual soils and (2) estimate spatial variations in the weathering degree and bedrock depth of residual soils in Singapore, ranging from completely weathered soil to weathered rock. Finally, the feasibility of detecting bedrock depth in Bukit Timah granite was examined by several approaches based on (1) preselected , (2) normalized Rayleigh wave phase velocity (), and (3) average . The results of the field experiments showed that this combined noninvasive multichannel analysis of surface waves (MASW) method can be successfully used to determine the profile of residual soils, which includes approximate bedrock detection. The newly proposed average -based approach using the ratios of average values of top soil layers (10–40 m) especially appears to be a simple, automatic, objective, and standardized method to identify depth to bedrock (within about 5-m resolution), which is confirmed by conventional boring investigations.
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Acknowledgments
The authors appreciate the financial support from Singapore Land Transport Authority (LTA, Award Number R-302-000-164-490).
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 143 • Issue 7 • July 2017
Copyright
©2017 American Society of Civil Engineers.
History
Received: Jun 13, 2016
Accepted: Nov 16, 2016
Published ahead of print: Mar 6, 2017
Published online: Mar 7, 2017
Published in print: Jul 1, 2017
Discussion open until: Aug 7, 2017
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