In spite of advances in rock mechanics theory and practice, application of modem rock mechanics to rock engineering problems is still difficult because acquiring the necessary analysis for formulas is often impractical. Therefore, rock engineering must still apply empirical approaches, rules of thumb, knowledge of plausible failure modes, and the designer's intuition and artistry.
Great advances have been made in rock mechanics, and we are beginning to have a good understanding of rock behavior. One could say that rock mechanics has reached a level of maturity. Yet there are limits to the applicability of rock mechanics to real rock engineering problems. These limits are set by the nature and extent of engineered rock structures, the variability of rock masses, and our general inability to obtain sufficient rock mass data for complete and rigorous analysis. This paper examines the relationships between engineering geology, the science of rock mechanics, and the application of rock engineering for practical design of rock structures. Methods of design are presented that will permit safe and economical design and construction of rock structures in the face of limited data. The paper is limited to civil engineering applications; problems of petroleum engineering, mining engineering, groundwater resource development, and hazardous waste applications are often of a different nature.