ABSTRACT
In ground investigations for identifying bearing stratum for structural foundations, typical methods include determining N-values via standard penetration tests and confirming geological conditions with boring cores. However, standard penetration tests, typically conducted at 1-meter intervals, make it difficult to detect local weaknesses in heterogeneous sand and gravel soils. To address this, we evaluated sand and gravel soils in pre-bridge construction geotechnical investigations using not only N-values and boring cores, but also X-ray CT analysis and density logs. X-ray CT analysis showed a correlation between CT values and actual ground density, allowing density to be calculated from CT data. This method confirmed that density can be estimated with relatively high accuracy using CT images. It was also noted that pore space between casing and borehole wall can slightly underestimate density in gravel soils when using density logs. Lastly, the correlation between CT-based density and N-values was examined, confirming that these density values help identify local soft spots in gravel soils.
