Understanding the geological and geotechnical characteristics of the shallow subsurface is of great importance for informed engineering decisions, particularly in regions like the Netherlands, where densely populated urban areas rest upon a complex stack of shallow subsurface sands, clays, and organics formed over the last ~100 Kyr. Of particular significance is the first sand layer under the Holocene sequence and its geomechanical properties, as it serves as a crucial foundation and water-bearing layer. Despite advancements in exploration techniques, the integration of geological and geotechnical data remains a challenge, hindering comprehensive subsurface characterization and parameterization.
This research addresses this integration gap by analysis of a dataset of nearly 200 Cone Penetration Test (CPT) and borehole pairs provided by TNO - Geological Survey of the Netherlands, penetrating the shallow subsurface up to depths of ~40 meters. On the borehole samples, multiple laboratory tests were conducted including laser diffraction particle size analysis, permeability, total porosity, wet and dry weights, geochemistry as well as macro and trace element composition.
All data was compiled into a database that was subsequently used to assess spatial variation and depositional patterns within naturally deposited sand formations. By integrating both borehole and CPT data, an improved understanding was gathered on the spatial extents and variation within the sand deposits. Subsequently, the results were evaluated in the context of engineering design, particularly for piled foundations and embankments, as the geotechnical properties and stratigraphy of the sand deposits have a significant effect on their geotechnical design. Ultimately, the paper aims to demonstrate how improved engineering designs can be developed by effectively integrating geological and geotechnical knowledge.