This book describes a unique approach using the principles of rock fracture mechanics to investigate the behaviour of fractured rock masses for rock engineering purposes. Rock fracture mechanics, a promising outgrowth of rock mechanics and fracture mechanics, has developed rapidly in recent years, driven by the need for in-depth understanding of rock mass failure processes in both fundamental research and rock engineering designs. Today, as rock engineering extends into many more challenging fields (like mining at depth, radioactive waste disposal, geothermal energy, and deep and large underground spaces), it requires knowledge of rock masses, complex coupled thermalhydraulicchemicalmechanical processes. Rock fracture mechanics play a crucial role in these complex coupled processes simply because rock fractures are the principal carrier and common interface. To date, the demand for rock fracture mechanicsbased design tools has outstripped the very limited number of numerical tools available.