Comparison of post-failure strength of micro-cracked marble with Hoek-Brown failure criterion

Year 2020, Volume: 26 Issue: 8, 1365 - 1372, 10.12.2020

Yılmaz Mahmutoğlu Gökhan Şans

Abstract

Failure criteria of rock mass is the most important base for designing of surface and underground structures. However, behavior of jointed rock mass and its failure criteria are the controversial subjects of rock mechanics. Main reasons for this discussion are problems during or after the geotechnical application. However, some of the experimental and theoretical approaches are often preferred as they are practical, compatible with engineering considerations, and assist in decision-making process. On the other hand, the differentiation in the scale of the geosystem, which varies depending on the scale of geotechnical application, building process, and time, means that the failure conditions will also change. It is clear that the Mohr-Coulomb failure criterion, which is widely used in practice, cannot exactly represent discontinuous geo-environments (fractured rock) consisting of joint systems. Since the rock generally has a discontinuous character, it has been researched since the 1970s, and the Hoek-Brown failure criterion, put forth in the 1980s and modified many times until today, is widely accepted in application. Nevertheless, it is known that the empirical parameters used in this failure criteria proposed for different types of rocks are also open to discussion. In this paper, the results of the mechanical tests conducted on the previously-fissured model material, which is physically similar to rock mass are discussed. Marble samples whose grain boundaries were disturbed by cyclic thermal treatment were used as the model material. Post-failure curves of model material obtained from continuous failure state triaxial tests were compared with Hoek-Brown Failure Criteria. In conclusion, it was shown that the failure envelopes representing intergranular failure in the post-failure phase were similar and comparable to the Hoek-Brown Failure Criterion. However, it is found out that the post-failure strength in low confining stress may be lower than that of estimation by the Hoek-Brown criterion. Experimental studies have also shown that intergranular failure will develop among structural weaknesses in rock masses, and therefore the strength parameters commonly used in practice will depend on the size of geo-application.

Keywords

Continuous failure state triaxial test, Hoek-Brown failure criterion, Post-failure, Rock mass

References

• [1] Mahmutoglu Y. “Mechanical behaviour of cyclically heated fine-grained rocks”. Rock Mechanics and Rock Engineering., 31(3), 169-179, 1998.
• [2] Mahmutoglu Y. The effects of strain rate and saturation on a micro-cracked marble. Engineering Geology, 82, 137-144, 2006.
• [3] Hamdi P, Stead D and Elmo D. “Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach”. Journal of Rock Mechanics and Geotechnical Engineering, 7(6), 609-625, 2015.
• [4] Chen W and Konietzky H. “Simulation of heterogeneity, creep, damage and lifetime for loaded brittle rocks”. Tectonophysics, 633, 164-175, 2014.
• [5] Hoek E and Brown ET. Underground Excavation in Rock. 1st ed. London, The Institute of Mining and Metallurgy, 1980.
• [6] Hoek E, Torres CC, Corkum B. “Hoek-Brown failure criterion” - 2002 Edition. In Proceedings of 5th North American Rock Mechanics Symposium, Toronto, Canada, 7-10 July 2002.
• [7] Hoek E. “Strength of rock and rock masses”. ISRM News Journal, 2(2), 4-16, 1994.
• [8] Hoek E, Kaiser PK, Bawden WF. Support of Underground Excavations in Hard Rock. Rotterdam, Netherlands, Balkema, 1995.
• [9] Hoek E, Marinos P, Benissi M. “Applicability of the geological strength index (GSI) classification for very weak and sheared rock masses. The case of the athens schist formation”. Bulletin of Engineering Geology and the Environment, 57(2), 151-160, 1998.
• [10] Hoek E and Marinos P. “Predicting tunnel squeezing problems in weak heterogeneous rock masses”. Tunnels and Tunnelling International, 132(11), 45-51, 2000.
• [11] Marinos P, Hoek E. “GSI: A Geological Friendly Tool for Rock Mass Strength Estimation”. Proceedings of the International Conference on Geotechnical and Geological Engineering (GeoEng 2000), Melbourne, Australia, 19-24 November, 2000.
• [12] Marinos P, Hoek E. “Estimating the geotechnical properties of heterogeneous rock masses such as flysch”. Bulletin of Engineering Geology and the Environment, 60(2), 85-92, 2001.
• [13] Marinos V, Carter TG. “Maintaining geological reality in application of GSI for design of engineering structures in rock”. Journal of Engineering Geology, 239, 282-297, 2018.
• [14] Hoek E, Brown ET. “The Hoek-Brown failure criterion and GSI-2018 edition”. Journal of Rock Mechanics and Geotechnical Engineering. 11, 445-463, 2019.
• [15] Zhao J. “Applicability of Mohr-Coulomb and Hoek-Brown strength criteria to the dynamic strength of brittle rock”. International Journal of Rock Mechanics and Mining Sciences, 37(7), 1115-1121, 2000.
• [16] Ghazvinian AH, Fathi A, Moradian ZA. “Failure behavior of marlstone under triaxial compression”. International Journal of Rock Mechanics and Mining Sciences, 45(5), 807-814, 2008.
• [17] Pariseau WG. “Fitting failure criteria to laboratory strength tests”. International Journal of Rock Mechanics and Mining Sciences., 44(4), 637-646, 2007.
• [18] Eberhardt E. “The Hoek-Brown Failure Criterion”. Rock Mechanics and Rock Engineering, 45, 981-988, 2012.
• [19] Hoek E. Practical Rock Engineering. e-book, 2007.
• [20] Brown ET. “Estimating the mechanical properties of rock masses”. Editors: Potvin Y, Carter J, Dyskin A, Jeffrey R., Proceedings of the Firsth Southern Hemisphere International Rock Mechanics Symposium, Australian Centre for Geomechanics, 3-22, Perth: Australian Centre for Geomechanics, Australia, 16-19 September, 2008.
• [21] Kovári K, Tisa A, Attinger O. “The concept of ‘‘continuous failure state’’ triaxial tests”. Rock Mechanics and Rock Engineering, 16(2), 117-131, 1983.
• [22] Rayleigh Lord. “The bending of marble”. Proceedings of Royal Society of London, London, England, 12 May 1934.
• [23] Rosengreen KJ, Jaeger JC. “The mechanical properties of an interlocked low-porosity aggregate”. Geotechnique, 18, 317-326, 1968.
• [24] Carfagni GR. “On the thermal degradation of marble”. International Journal of Rock Mechanics and Mining Sciences, 36, 119-126, 1999.
• [25] Weiss T, Siegesmund S, Pasolofosaon PNJ. “Ultrasonic wave velocities as a diagnostic tool for quality assessment of marble”. Geological Society London Special Publications, 205(1), 149-164, 2002.
• [26] Mahmutoglu Y. “Prediction of weathering by thermal degradation of a coarse-grained marble using ultrasonic pulse velocity”. Environmental Earth Sciences, 76, 435-455 2017.
• [27] Kovári K, Tisa A, Einstein HH, Franklin, JA. “Suggested methods for determining the strength of rock materials in triaxial compression”. International Journal of Rock Mechanics and Mining Sciences, Geomechanics Abstracts, 20(20), 283-290, 1983.
• [28] ISRM. The Complete ISRM Suggested Methods for Rock Characterization, Testing and Monitoring. 1974-2006. Editors: Ulusay, R. and Hudson JA. Suggested Methods Prepared by the Commission on Testing Methods, International Society for Rock Mechanics, Compilation Arranged by the ISRM Turkish National Group, 159-164, Ankara, Turkey, Kozan, 2007.
• [29] Hoek E, Brown ET. “Practical estimates of rock mass strength”. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts, 34(8), 1165-1186, 1997.