ROCK TUNNELLING | ROCK MASS CLASSIFICATION - REVIEW


Table 1: 37 Rock mass classification systems (RMCS) compiled through literature study and an international survey Abbrev.


System full name


A-BQ ARMR BQ C


CMRR CSMR1 CSMR2 f


GBI GI


GSI


GSR IMS


IRMR I


Anisotropic—basic quality Anisotropic rock mass rating Index of rock mass basic quality Kiruna factor


Coal mine roof rating Chinese system for SMR


Continuous slope mass rating Protodyakonov coefficient Geotechnical blockiness index Geological indication


Geological strength index Geophysical strata rating


In-situ rock mass rating


I-System I-system MQD


MRMR M-RMR N


N'


NATM Q


Q-slope RMi


RMQR RMR RMS RQD RSR SIA


SMR


SRMC SRMR SSAM SSPC SSR TSR


Marble quality designation Mining rock mass rating


Modified rock mass classification Rock mass number


Modified stability number Survey


Yes Yes Yes Yes No


Yes Yes No No


Yes Yes No No No No No


Yes Yes Yes No


NATM geomechanics rock mass classification Yes Q-system Q-slope


Rock mass index


Rock mass quality rating Rock mass rating Rock mass strength


Rock quality designation Rock structure rating SIA 197


Slope mass rating


Sydney rock mass classification Slope rock mass rating


Slope stability assessment methodology Slope stability probability classification Slope stability rating Total stability rating


Yes Yes Yes Yes Yes Yes Yes Yes No


Yes No


Yes Yes Yes Yes No


Guo et al. (2020)


Saroglou et al. (2029) Lin (1998)


Hansagi (1965)


Molinda and Mark (1994) Chen (1995)


Tomás et al. (2007)


Protodyakonov (1926), see, e.g., Ji et al. (2023) Walker and DeBruyn (2006) Reinhold et al. (2017) Hoek and Brown (1997)


Medhurst and Hatherly (2005) McFeat-Smith & Harman (2004) Jakubec and Laubscher (2000) Bineshian (2019) Chan et al. (1994) Laubscher (1977) Ünal (1996)


Goel et al. (1995)


Mathews et al. (1981) ÖGG (2023)


Barton et al. (1974) Barton and Bar (2015) Palmstrøm (1995) Aydan et al. (2014) Bieniawski (1973) Selby (1980) Deere (1964)


Wickham et al. (1972) SIA 197 (2023) Romana (1985) Pells et al. (1978) Robertson (1988)


McQuillan et al. (2018) Hack (2002)


Taheri and Tani (2007) Benumof and Griggs (1999) Efforts to construct a ‘family tree’ of rock mass


classification systems have highlighted the existence of five main strands, illustrating both the pioneering figures behind these systems and their interconnected evolution that often gave rise to multiple follow-up RMCS. These strands are: (i)


the rock load classification system strand (dark red in Figure 1) being the base for/or influencing six follow-up systems;


(ii) RQD strand (green in Figure 1) being the base for/ or influencing five follow-up systems;


(iii) RMR strand (blue in Figure 1) being the base for/or influencing 17 follow- up systems among which the SMR and SRMR served as a base for further RMCS themselves (marked as brown and orange strands in Figure 1);


(iv) Q-strand (purple in Figure 1) being the base for/or influencing 11 follow-up systems; and,


18 | June 2025


3 SURVEY METHODOLOGY Two surveys were conducted with the online tool ‘Microsoft Forms’. The surveys followed two goals: (i) investigate the international distribution of RMCS; and, (ii) identify RMCS that the authors were unaware of before. Both surveys were identical in their setup and comprised one main question and three choices: ● Main question and description: “Which rock mass classification system have you used in this country the most?” A description was given that specifies: “Please select a rock mass classification system, a country and an application below. You will be able to submit multiple answers for different systems.”


● Choice 1: “Select a rock mass classification system (alphabetically sorted) or enter a new one”. Here, participants could choose one of the RMCSs of Table 1 which are indicated as ‘yes’ in the column “Included in survey questions”. These are the systems that the survey authors originally included in their questionnaire. Participants also had the choice to indicate “other” and specify a new RMCS (indicated as ‘no’ in the column “Survey” in Table 1).


As mentioned above, the A-BQ system lies on its own path and can be seen as a solitary development that only recently merged with the RMR strand. The same goes for the rock mass classification


according to the ‘ÖGG geomechanical design’ guideline that goes back to the ‘Gebirgsgüteklassen’ that was introduced in the ÖNORM B 2203 (1975) and is connected to the New Austrian Tunnelling method. The ‘ÖGG geomechanical design’ is generally different from other RMCS, as it is based on the idea that every rock mass is unique and should get its own classification to be able to account for different failure modes and not oversimplify the geology to one single number. The ‘Geological Indication’ (GI) from Reinhold et al. (2017) is one recent offspring of this concept and constitutes a rock mass behaviour-based RMCS developed for one construction lot of the Brenner Base Tunnel project. The historical reconstruction shows that system


development took a significant upturn between 1970 and 2000, with 21 RMCS developed in that timeframe. Many of these systems are still in use today and formed the basis for more application-specific systems developed in the last two decades. It needs to be noted that a certain subjective


assessment affects the design of the whole family tree, as many authors of RMCS do not explicitly write which prior systems have had the primary influence on their work. Furthermore, several systems have only been published as part of conference proceedings, severely limiting their accessibility, and their origin had to be retraced through third-party literature. Lastly, even though we see the compilation of RMCS in Table 1 as one of the most comprehensive ones up to today, it cannot be ruled out that even more RMCS exist.


References


(v) GSI strand (light green in Figure 1) being the base for/or influencing at least two more systems.


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