ABSTRACT
Swelling and disintegration behaviors in rock masses are common phenomenon in the Andean Region, due to the presence of volcano-sedimentary formations containing swelling clays and other degradable minerals like zeolites. Hence, a comprehensive rock mass characterization must be conducted to evaluate the rheological risk of any underground work located on this kind of geological environment. This characterization should be based in fast and reliable laboratory tests, like Ethylene Glycol, Atterberg Limits, Methylene Blue, and the Point Load Test Strength Index. Incorporating in one index only the information provided by these tests, it is proposed a Degradation Index that can evaluate the risk of swelling and disintegration. This paper presents the development of the Degradation Index and a validation with hydro tunnels that experienced rock support damages and collapses. The validation showed a very good correlation between the Degradation Index and damages in the rock support.
