Swelling Rocks Investigation on Hydro Tunnels – A Comprehensive Characterization based on Laboratory Tests and Constitutive Models
Swelling of rocks is a common phenomenon in the Andean Region, due to the presence of volcano-sedimentary units containing clays, typically from the smectite group as part of the rock matrix. Hence, a comprehensive rock mass characterization has to be made in order to evaluate the risk of underground works located in this kind of geological environment. For hydro tunnels in South America, a set of swelling pressure tests of different type (on intact rock discs, ground rock powder, cyclic loading and triaxial tests) were executed for swelling potential evaluation. The results show that obtained values are highly dependent on test procedures, suggesting that swelling pressure test has to be considered as an index, instead of a definitive value of pressure (especially when using ground rock powder). A result comparison and discussion is included in this paper and recommendations for engineering design are provided based on numerical modelling.