Abstract The application of existent rock mass classifications in Taiwan is introduced. The applicability of these classifications in rock or poor-cemented ground tunnels is discussed. A new classification system is established，which classifies rock formations in Taiwan into four types. This system is based on local geologic material properties，geologic age，sensitivity to water and relevant strength characteristics of rock formations. The criteria to rate various rock types are also formulated，which are the basis of tunnel-support design.
2004, Vol. 23 
