ABSTRACT
Three-dimensional excavations include caverns such as hydroelectric machine halls for civil engineering purposes and stopes in hardrock mines. Failures on geologic structures such as joints that intersect excavation walls may be anticipated in a similar manner using joint strength properties and joint stresses in analogous safety factor calculations. Analysis for wall joint safety requires estimation of two numbers, joint shear strength, and joint shear stress. Shear strength relates to joint properties and may be considered known for design analysis. Tabular excavations such as hardrock stopes and softrock panels may be flat, dipping, or vertical and pose a special challenge even for direct numerical calculations. Pillars are the primary defense against opening collapse, but local support and reinforcement are also required for safety. Cemented fill is used for subsidence control over abandoned room and pillar mines in many cases. Cable bolts may be tensioned during the installation process to obtain immediate support action.
