Reduction of Q-Barton Uncertainty: Proposal of a New Methodology Based on a Factual Geological–Geotechnical Database to Apply in Tunnels
Source abstract
Abstract
The main goal of this study is to analyse and quantify errors, doubts, and uncertainties associated with the use of Q-Barton system parameters. This study also analyses how related factors influence the observer in tunnel openings. Data from six penstock tunnels of an underground hydraulic circuit at a hydroelectric power plant were used to study the application of the Q-Barton index. Records of values adopted at tunnel opening faces were compared with values calculated and quantified objectively. The values adopted by a geologist at the tunnel opening (Q-Barton-geologist) were compared with statistical values of the Q-Barton (Q-Barton-GGDB) generated from a factual database. This comparison enables the evaluation of the accuracy and influence of the Q-Barton system in tunnel openings, as well as the consequences on labour days and geotechnical support costs associated with a structure represented by the sample used. Using Q-Barton-GGDB, savings of 17.5% on geotechnical supports and 12.9% on labour days will be achieved. Final results highlight the need to explore the issues discussed here further.
Source: crossref · Quality: baseline
Research context
OpenAlex topics: Rock Mechanics and Modeling · Geotechnical Engineering and Analysis · Drilling and Well Engineering
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
CCT—Earth Sciences Centre, University of Minho, 4710-057 Braga, Portugal
CONGEO, Consultores de Geologia, Lda., 4400-285 Vila Nova de Gaia, Portugal
Independent Researcher, 4200-465 Porto, Portugal
FEUP—Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal
GEG, Gabinete de Estruturas e Geotecnia, Lda., 4200-024 Porto, Portugal
References (35)
Show source-provided references
1. Engineering classification of rock masses for the design of tunnel support10.1007/BF01239496 ↗
2. Some new Q-value correlations to assist in site characterisation and tunnel design10.1016/S1365-1609(02)00011-4 ↗
3. Barton, N., and Grimstad, E. (1994, January 13–14). The Q-system following Twenty Years of Application in NMT Support Selection. Proceedings of the 43rd Geomechanik Colloquy, Feldsbau, Salzburg, Austria.
4. NGI (2025). Using the Q-System, Rock Mass Classification and Support Design, Norwegian Geotechnical Institute.
5. Use and misuse of rock mass classification systems with particular reference to the Q-System10.1016/j.tust.2005.10.005 ↗
6. Lessons learned from field measurements in tunnelling10.1016/S0886-7798(98)00004-2 ↗
7. Empirical methods of calculating the mechanical parameters of the rock mass
8. Discontinuity spacing and RQD estimates from finite length scanlines10.1016/0148-9062(84)90797-6 ↗
9. Kirkaldie, L. (1988). The Rock Quality Designation (RQD) Index in Practice. Rock Classification Systems for Engineering Purposes, ASTM. ASTM STP 984.10.1520/STP984-EB ↗
10. Measurements of and Correlations between Block Size and Rock Quality Designation (RQD)10.1016/j.tust.2005.01.005 ↗
11. Onsel, I.E., Ozturk, C.A., Ozkan, M., and Nasuf, S.E. (2011, January 26–29). Software for RQD and rock mass evaluation. Proceedings of the US Rock Geomechanics Symposium (ARMA 11-320), San Francisco, CA, USA.
12. Fault detection in 3D by sequential Gaussian simulation of Rock Quality Designation (RQD)10.1007/s12517-012-0633-3 ↗
13. Discontinuity spacing in rock10.1016/0148-9062(76)90818-4 ↗
14. Discontinuities and rock Mass Geometry10.1016/0148-9062(79)90001-9 ↗
15. The volumetric joint count—A useful and simple measure of the degree of rock jointing
16. Ewan, V., West, G., and Temporal, J. (1983). Variation in measuring rock joints for tunnelling, Morgan-Grampian Limited. Tunnels & Tunnelling International.
17. Sharma, V.M., and Saxena, K.R. (2001). Measurement and Characterization of Rock Mass Jointing. In-Situ Characterization of Rocks, A.A. Balkema Publishers.
18. Automated method for extracting and analysing the rock discontinuities from point clouds based on digital surface model of rock mass10.1016/j.enggeo.2018.03.020 ↗
19. Estimating the joint roughness coefficient of discontinuities found in metamorphic rocks10.1007/s10064-008-0151-4 ↗
20. Estimation of the Joint Roughness Coefficient (JRC) by visual comparison10.1007/s006030200009 ↗
21. Determination of parameters range in rock engineering by means of Random Set Theory10.1016/S0951-8320(00)00058-2 ↗
22. Bayesian methodology for updating geomechanical parameters and uncertainty quantification10.1016/j.ijrmms.2009.03.008 ↗
23. Extending the Q system’s prediction of support in tunnels employing fuzzy logic and extra parameters10.1016/j.ijrmms.2006.02.002 ↗
24. Incorporating parameter variability in rock mechanics analyses: Fuzzy mathematics applied to underground rock spalling10.1007/s00603-009-0034-4 ↗
25. Bedi, A. (2013). A Proposed Framework for Characterising Uncertainty and Variability in Rock Mechanics and Rock Engineering. [Ph.D. Dissertation, Imperial College London].
26. Monte Carlo simulation (MCS)-based uncertainty analysis of rock mass quality Q in underground construction10.1016/j.tust.2019.103089 ↗
27. Probabilistic estimation of ground condition and construction cost formountain tunnels10.1016/j.tust.2014.02.014 ↗
28. Challenge problems: Uncertainty in system response given uncertain parameters10.1016/j.ress.2004.03.002 ↗
29. Deere, D.U. (1963). Technical description of rocks cores for engineering purposes. Rock Mech. Eng. Geol., 116–122.
30. ISRM—International Society of Rock Mechanics (1978). Suggested methods for the quantitative description of discontinuities in rock masses. Int. J. Rock Mech. Min. Sci. Geom. Abstr., 15, 319–368.
31. ISRM—International Society of Rock Mechanics (1981). Basic geotechnical description of rock masses (BGD). Int. J. Rock Mech. Min. Sci. Geom. Abstr., 18, 85–110.10.1016/0148-9062(81)90277-1 ↗
32. Sousa, J. (2016). A Geologia da Frente de Túneis e Suas Implicações Nas Incertezas do Cálculo do Sistema Q-Barton. [Master’s Thesis, University of Porto]. (In Portuguese).
33. Palmström, A. (1995). RMi—A Rock Mass Characterization System for Rock Engineering Purposes. [Ph.D. Thesis, University of Oslo].
34. The shear strength of rock joints in theory and practice10.1007/BF01261801 ↗
35. Barton, N., and Bieniawski, Z.T. (2008). RMR and Q–Setting records straight. Tunn. Tunn. Intern., 26–29.