EFFECTS OF WEATHERING AND ALTERATION ON POINT LOAD AND SLAKE DURABILITY INDICES OF QUESTA MINE MATERIALS, NEW MEXICO

摘要

Point load strength (Is50) and slake durability (ID_2) indices provide a measure of the strength and durability of rock fragments and are related to the alteration intensity and frictional resistance of the materials. Samples were collected from the rock piles, alteration scars and debris flows at the Questa mine with the purpose of examining relationships between ls50 and ID_2, mineralogy, chemistry, weathering, hydrothermal alteration, and other geotechnical parameters. The ls50 from the various rock piles ranges from 0.6-8.2 MPa and the ID_2 ranges from 80.9-99.5%. The ls50 and ID_2 results indicate that the samples from the debris flows are stronger (average ls50= 4.0 MPa and ID_2= 98.4%) than the rock-pile samples and that the alteration scar samples are weaker (average ls50 = 2.8 MPa and ID_2 = 89.2%) than the rock-pile samples, but still most of these rocks are strong in terms of their ls50 and ID_2. The ls50 decreases as the degree of alteration increases in some rock pile and alteration scar samples, but not in all. However, the majority of the rock fragments within the rock piles still indicate high strength, even after 25-40 years of weathering.