The Q-system of rock mass classification was developed in Norway in 1974. The system was developed on the basis of an analysis of 212 tunnel case histories from Scandinavia. It is a quantitative classification system and is an engineering system facilitating the design of tunnel supports. Q-system use six different parameters to asses the rock mass quality. The parameters are:

• RQD
• Number of joint sets Jn
• Roughness of the most unfavorable joint or discontinuity Jr
• Degree of alteration of filling along the weakest joint Ja
• Water inflow Jw
• Stress condition SRF