Atterberg Limits of Two Crushed and Natural Glauconite Soils

Glauconite is the name of a mineral and soil containing significant quantities of iron and potassium varying in color from green to black, linked to its geological history. These soils are problematic in nature and exhibit potentially hazardous responses related to the construction of foundations. This is in part due to the difficulties in quantifying their geotechnical properties and how easily these properties change. Sand-sized glauconitic particles are often fractured, which increases their crushability, transitioning from sand-sized to fine-grained particles with cohesive behavior. This has led to geotechnical challenges including difficulty in pile driving and the potential for refusal. Glauconite has been shown to adhere to pile walls, which increases pile driving resistance. This may be a problem as glauconite deposits can be found along the eastern coast of the US in offshore wind lease areas. In this study, two glauconitic sands from the East Coast of the US are investigated for differences in their Atterberg limits in their natural and crushed state to quantify the increases of plasticity. Results on samples from the Late Cretaceous Navesink and Paleogene Hornerstown formations illustrate how sample preparation and particle crushing increases plasticity and changes USCS classification of glauconite soils. Additionally, it was found that these specific soils are acidic and when crushed their acidity levels and their colors can change.