Shale Durability Rating System Based on Loss of Shear Strength

Abstract

A durability rating system is developed to assist in the classification of shale that is to be used in compacted embankments. The system is based on the loss of shear strength due to the intrusion of water. Nine different shales are assigned relative durability ratings based on consolidated undrained triaxial shear‐strength tests. Companion tests are performed, one using water as the pore fluid and one using silicon oil. The mathematical difference between the results of the two tests is used to quantify the shear strength loss due to the action of water, and to assign relative durability ratings. The shales are also subjected to five simple index tests that have been previously shown to correlate well with durability. The results of the simple tests are correlated with the results of the shear strength tests through use of multiple regression techniques. Equations are developed in which the durability ratings could be estimated from the results of the simple index tests. The new system is compared to other shale rating systems.