Q-system

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For the linguistics formalism, see Q-systems.

The Q-system of rock mass classification was developed in Norway in 1974 by Nick Barton, Lien, R., and Lunde, J at NGI (Norwegian Geotechnical Institute). 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 assess the rock mass quality. The parameters are:

  • Rock Quality Designation RQD
  • Joint set number Jn
  • Roughness of the most unfavorable joint or discontinuity Jr
  • Degree of alteration of filling along the weakest joint Ja
  • Water inflow Jw
  • Stress Reduction Factor SRF

The Q-factor can then be calculated as:

Q=\frac{RQD}{J_n}\frac{J_r}{J_a}\frac{J_w}{SRF}