Geotechnical comparison of weathering degree and shear wave velocity in the decomposed granite layer in Hongseong, South Korea
2015
Sun, Chang-Guk | Kim, Bo-Hyun | Park, Ka-Hyun | Chung, Choong-Ki
As part of a fundamental characterization of a subsurface layer in South Korea, the weathering degree and shear wave velocity (V S) were evaluated in a decomposed granite in Hongseong, using X-ray fluorescence analyses and site investigations, including borehole drilling with standard penetration test (SPT) and in situ seismic tests. The subsurface layer was composed of a weathered layer 10–40 m thick at most sites. Weathering degree analyses indicated that three chemical weathering indices, the modified weathering potential index (MWPI), Vogt ratio (VR), and weathering index of Parker (WIP), generally increased with decreasing depth. In situ seismic tests revealed that V S ranged between 200 and 500 m/s in the weathered layer. Using the V S and N values from the SPT at borehole seismic testing sites, correlations between V S and N values were established for the weathered layer. Furthermore, examination of the relationships of the V S and N values with the MWPI, WIP, and 100/VR indices showed that the index values increased linearly with increasing V S and exponentially with increasing N values.
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