Shear Behavior of Weathered Compacted Shales

Shale is the most frequently encountered material in civil infrastructure works. It constitutes about 70% of subsurface materials around the world. These materials cause problems because they tend to degrade with time due to weathering. Degradation results in the shale deteriorating from a hard rock-like material with high frictional resistance to a soft fine-grained soil mass with lower shear strength and high deformability. Therefore, common problems associated with embankments constructed with compacted shales include excessive settlement, and local and global instabilities. This paper presents the results of consolidated undrained triaxial tests performed on compacted weathered shale at different compaction energies. The triaxial tests analysis showed that compacted shale can behave as normally consolidated material, slightly over consolidated material, or heavily over consolidated material depending on the energy of compaction and the effective consolidation pressure. Also, for this work characteristics of the stress paths were analyzed in order to evaluate the shear strength parameters obtained from various interpretations of shear strength.