: ''For the linguistics formalism, see
Q-systems
Q-systems are a method of directed graph transformations according to given grammar rules, developed at the Université de Montréal by Alain Colmerauer in 1967–70 for use in natural language processing. The Université de Montréal's machine t ...
.''
: ''For the genetic method, see
Q-system (genetics).''
The Q-system for rock mass classification is developed by Barton, Lien, and Lunde.
[ It expresses the quality of the rock mass in the so-called ''Q-value'', on which design are based and support recommendations for underground excavations.
The Q-value is determined with
::
The first term '' RQD'' ''(]Rock Quality Designation Core recovery parameters describe the quality of core recovered from a borehole.
Total core recovery
Total core recovery (TCR) is the borehole core recovery percentage.
TCR is defined as the quotient:
:TCR = \left(\frac\right)\times 100 %
:l_\ma ...
)'' divided by ''Jn (joint set number)'' is related to the size of the intact rock blocks in the rock mass. The second term ''Jr (joint roughness number)'' divided by ''Ja (joint alteration number)'' is related to the shear strength along the discontinuity planes and the third term ''Jw (joint water parameter)'' divided by ''SRF (stress reduction factor)'' is related to the stress environment on the intact rock blocks and discontinuities around the underground excavation.
A multiplication of the three terms results in the ''Q'' parameter, which can range between 0.001 for an exceptionally poor to 1000 for an exceptionally good rock mass. The numerical values of the class boundaries for the different rock mass qualities are subdivisions of the ''Q'' range on a logarithmic scale.
The Q-value determines the quality of the rock mass, but the support of an underground excavation is based not only on the ''Q-value'' but is also determined by the different terms in the above equation. This leads to a very extensive list of classes for support recommendations.
See also
* Rock Structure Rating Rock Structure Rating (RSR) is a quantitative method for describing quality of a rock mass and appropriate ground support, in particular, for steel-rib support, developed by Wickham, Tiedemann and Skinner.
The RSR concept introduced a rating syste ...
* Hoek-Brown failure criterion
* Rock mass rating The rock mass rating (RMR) is a geomechanical classification system for rocks, developed by Z. T. Bieniawski between 1972 and 1973.
Since then it has undergone multiple modifications out of which, RMR89 is commonly used. Recently RMR14 has been ...
References
Further reading
* Bieniawski, Z.T. "Engineering Rock Mass Classifications", John Wiley and Sons, New York, 1989
*
* Pantelidis, L (2009). "Rock slope stability assessment through rock mass classification systems", ''International Journal of Rock Mechanics and Mining Sciences'', 46(2), (315–325).
*{{Cite journal
, last1 = Palmstrom , first1 = A.
, last2 = Broch , first2 = E.
, year = 2006
, title = Use and misuse of rock mass classification systems with particular reference to the Q-system
, journal = Tunnelling and Underground Space Technology
, volume = 21
, number = 6
, pages = 575–593
, doi = 10.1016/j.tust.2005.10.005
Rock mass classification