Remains of subtropical deep weathered clay found in fracture and weakness zones in thebedrock in the Trøndelag area yields poor conditions for tunnel construction and have resultedin expensive difficulties for such projects. Smectite has a high swelling potential whenhydrated, which can induce swelling pressure and damage the structures it surrounds. Thisstudy was designed as an extension of a previous study performed at NTNU that showedambiguity between free swell and swelling pressure measurements. 55 samples exhibitingswelling behavior were obtained from old SINTEF projects. Swelling minerals were identifiedusing X-Ray diffraction and the fine particle fraction grain size distribution was measuredusing laser diffraction spectroscopy. Swelling potential was quantified using constant volumeoedometer testing and free swell tests. The potential of variance (r2) between mineral contentand maximum swelling pressure was 0.8. Free swell was less correlated with smectitecontent, yielding an r2 value of 0.4 and several outliers. Free swell was affected by otherphysical parameters in addition to smectite content. Additional tests, which could not beperformed due to limited sample material, are desired to better understand the physicalproperties behind each measure of swelling potential.