Tunnelling in difficult ground — Swelling behaviour and identification of swelling rocks

Summary This brief review first describes typical swelling phenomena in underground openings and then discusses in detail the underlying swelling mechanisms. Mechanical, osmotic and intracrystalline swelling in argillaceous ground, as well as hydration of anhydrite are described. The fact that many of these mechanisms interact and, particularly, that swelling and squeezing may occur simultaneously is emphasized. The paper concludes with a few comments on implications on analysis, design and construction.