Study on the swelling potential of some selected rocks

Abstract

For clay minerals the swelling mechanisms and factors influencing on the swelling potential is widely explained and confirmed through comprehensive research. When it comes to intact rocks there are questions regarding both swelling potential and main reasons for swelling in the different rock types. It is therefore important to better understand the swelling behaviour of different rocks rich in clay minerals when in contact with water. In this pretext, an extensive laboratory work has been performed to address a study on the expansive character of intact rock. Three different rock types have been tested; alum shale, greenschist and tuff, and the rocks vary in both structure and mineral composition. Three traditional test methods consisting swelling pressure determination using dust powder, rock cylinders and free swelling have been used. In addition, recently developed new test apparatus at NTNU/SINTEF lab has also been used. The benefit of this method is that it gives possibility to look on the swelling strain of rock cubes when submerged in all three directions. When exposed to water the displacement in all three directions is recorded over time. Results of all swelling test methods are compared. Further discussions are made on the swelling impact based on mineralogical composition. The applicability of this new method in comparisons to the other test methods is also discussed.