A SHALE RATING SYSTEM AND TENTATIVE APPLICATIONS TO SHALE PERFORMANCE

A "shale rating system" based on three properties-durability, strength, and plasticity-is proposed. A shale sample is assigned a rating value by first measuring its second-cycle slake-durability index. Rocklike shales that have durability values greater than 80 percent for this index are further characterized by measuring their point load strength. Soillike shales that have durability values of less than 80 percent are further characterized by mearsuring their plasticity index. The shale rating, derived from these test results by using a rating chart, is a continuously variable number in the 0.0-9.0 range. Tentative correlations (trend lines) are proposed that link this rating with aspects of engineering performance such as excavating mehtods (e.g., whether to dig or to blast), foundation properties (e.g., bearing capacities and foundation moduli), embankment construction (e.g., lift thicknesses and compaction methods), and slope stability (e.g., relations between slope height and angle and failure mechanisms).