An Experimental Study to Determine the Hoek-Brown Constant (mi) for Tuffs

Year 2021, Volume: 42 Issue: 1, 52 - 69, 22.04.2021

Serdar Yaşar

https://doi.org/10.17824/yerbilimleri.771224

Abstract

Nonlinear strength criteria are handy tools for determining the whole range of rock material behavior such as tensile, unconfined compressive, confined compressive and brittle-ductile transition. Hoek-Brown (H-B) failure criterion is one of the most widely used strength criteria for the intact rock material and mi constant is an important parameter of the H-B criterion. The mi constant in the H-B criterion can be determined from reference tables, triaxial compression tests and empirical studies for different rock materials. However, experimental studies for determining the mi constant for tuffs are limited. On this context, a series of triaxial compressive strength tests were carried out on two different tuff samples under varying confining pressures. Using the least squares regression, H-B criterion parameters were computed. As a result, it was seen that computed mi constants were lower than the tabulated constants and unconfined compressive strength of the tuffs were overestimated by the H-B equation. Furthermore, post-failure images of the samples indicated that failure angle increased with increasing confining pressure.

Keywords

Rock mechanics, Hoek-Brown failure criterion, Triaxial compression test, Confining pressure, mi constant

Thanks

I would like to acknowledge Kubilay ALKAN and Mehmet ARSLAN for their efforts during experimental studies.

Tüflerin Hoek-Brown Sabitinin (mi) Belirlenmesi için Bir Deneysel Çalışma

Abstract

Lineer olmayan yenilme ölçütleri, kaya malzemelerinin çekme, basma, yanal basınç altında basma ve kırılgan-sünek geçişi gibi tüm aşamalarını temsil etme noktasında kullanışlı araçlardır. Hoek-Brown (H-B) yenilme ölçütü sağlam kaya malzemesi için önerilmiş olan en önemli ölçütlerden birisidir ve mi sabiti ölçütün önemli bir parçasıdır. Hoek-Brown yenilme ölçütünde farklı kaya malzemeleri için mi sabiti çizelgede önerilen değerlerden, üç eksenli basınç deneylerinden ya da görgül çalışmalardan belirlenebilmektedir. Ancak tüflerin mi sabitinin belirlenebilmesi için yapılan deneysel çalışmalar sınırlıdır. Bu amaçla, iki farklı türde tüf örnekleri üzerinde farklı yanal basınçlar kullanılarak bir seri üç eksenli basınç dayanımı deneyleri gerçekleştirilmiştir. En küçük kareler regresyon yöntemini kullanarak H-B yenilme ölçütünün parametreleri tespit edilmiştir. Sonuç olarak, tespit edilen mi değerlerinin tabloda verilen değerden daha düşük olduğu belirlenmiştir. Ayrıca, tek eksenli basınç dayanımı değerinin H-B denklemi ile gerçek değerden daha yüksek olarak hesaplandığı görülmüştür. Buna ek olarak, yenilme sonrası numune görüntüleri, yenilme açısının artan yanal basınç ile arttığını göstermiştir.

Keywords

Kaya mekaniği, Hoek-Brown yenilme ölçütü, Üç eksenli basınç deneyi, Yanal basınç, mi sabiti

References

• Aladejare, A. E., Wang, Y., 2019. Probabilistic Characterization of Hoek–Brown Constant mi of Rock Using Hoek’s Guideline Chart, Regression Model and Uniaxial Compression Test. Geotechnical and Geological Engineering, 37, 5045–5060.
• Andreev, G. E., 1995. Brittle Failure of Rock Materials. A.A. Balkema.
• Arshadnejad, S., Nick, N., 2016. Empirical models to evaluate of “mi” as an intact rock constant in the Hoek-Brown rock failure criterion. 19th Southeast Asian Geotechnical Conference, 943-948.
• Byerlee, J. D., 1968. Brittle-Ductile Transition in Rocks. Journal of Geophysical Research, 73, 14, 4741-4750. Cai, M., 2010. Practical Estimates of Tensile Strength and Hoek–Brown Parameter mi of Brittle Rocks. Rock Mechanics and Rock Engineering, 43, 2, 167-184.
• Cai, M., Kaiser, P.K., Tasaka, Y., Minami, M., 2007. Determination of Residual Strength Parameters of Jointed Rock Masses Using the GSI System, International Journal of Rock Mechanics and Mining Sciences, 44, 247-265.
• Griffith, A. A., 1921. The Phenomena of Rupture and Flow in Solids. The Philosophical Transactions of The Royal Society, 221 A, 163-198.
• Hoek, E., 1965. Rock Fracture under Static Stress Conditions. CSIR Report, s. 363.
• Hoek, E., 1983. Strength of Jointed Rock Masses, 23rd. Rankine Lecture. Géotechnique, 33, 187–223.
• Hoek, E., 1994. Strength of Rock and Rock Masses. ISRM News Journal, 2, 2, 4-16.
• Hoek, E., 2007. Practical Rock Engineering, E-Book, s. 341.
• Hoek, E., Brown, E. T., 1980. Empirical Strength Criterion for Rock Masses. Journal of the Geotechnical Engineering Division, 106 (GT9), 1013-1035.
• Hoek, E., Carranza-Torres, C.T., Corkum, B., 2002. Hoek-Brown Failure Criterion, 2002 Edition. Fifth North American Rock Mechanics Symposium, University of Toronto Press, Toronto, 267-273.
• Hoek. E., Martin, C. D., 2014. Fracture Initiation and Propagation in Intact Rock. Journal of Rock Mechanics and Geotechnical Engineering, 6, 287-300.
• Hoek, E., Brown, E. T., 2019. The Hoek–Brown Failure Criterion and GSI – 2018 Edition. Journal of Rock Mechanics and Geotechnical Engineering, 11, 3, 445-463.
• ISRM, 2007. The Complete ISRM Suggested Methods for Rock Characterization, Testing and Monitoring:1974-2006, Edited by R. Ulusay and J.A. Hudson.
• Labuz, J. F., Zang, A., 2012. Mohr–Coulomb Failure Criterion. Rock Mechanics and Rock Engineering 45, 975–979.
• Lade, P. V., 1993. Rock Strength Criteria–The Theories and Evidence. Comprehensive Rock Engineering, Pergamon Press, Oxford, Vol.1, 255-284.
• Lakirouhani, A., Hasanzadehshooiili, H., 2011. Review of Rock Strength Criteria. 22nd World Mining Congress & Expo, Istanbul, 1-10.
• Mostyn, G., Douglas, K. J., 2000. Strength of Intact Rock and Rock Masses. International Conference on Geotechnical and Geological Engineering, Vol. 1, Technomic Publishing, 1389–1421.
• Murrell, S. A. F., 1958. The strength of Coal under Triaxial Compression. Mechanical Properties of Non-Metallic Brittle Materials, London, 123-145.
• Read, S., Richards, L., 2014. Correlation of Direct and Indirect Tensile Tests for Use in the Hoek-Brown Constant mi. Rock Engineering and Rock Mechanics: Structures in and on Rock Masses. Taylor and Francis, London.
• Richards, L., Read, S., 2011. A Comparative Study of mi, The Hoek-Brown Constant for Intact Rock Material. 45th US Rock Mechanics/Geomechanics Symposium. American Rock Mechanics Association, San Francisco, CA.
• Sari, M., 2010. A Simple Approximation to Estimate the Hoek–Brown Parameter “mi” for Intact Rocks. Rock Mechanics in Civil and Environmental Engineering. Taylor and Francis, London.
• Shen, J., Karakus, M., 2014. Simplified Method for Estimating the Hoek-Brown Constant for Intact Rocks. Journal of Geotechnical and Geoenvironmental Engineering, 140, 6, 04014025, 1-8.
• Shen, B., Shi, J., Barton, N., 2018. An Approximate Nonlinear Modified Mohr-Coulomb Shear Strength Criterion with Critical State for Intact Rocks. Journal of Rock Mechanics and Geotechnical Engineering, 10, 4, 645-652.
• Sönmez, H., Ulusay, R., 2002. A Discussion on the Hoek-Brown Failure Criterion and Suggested Modifications to the Criterion Verified by Slope Stability Case Studies. Yerbilimleri, 26, 77-99.
• Vásárhelyi, B., Kovács, L., Török, Á., 2016. Analysing the Modified Hoek-Brown Failure Criteria Using Hungarian Granitic Rocks. Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 2, 131–136.
• Wang, W., Shen, J., 2017. Comparison of Existing Methods and A New Tensile Strength Based Model in Estimating the Hoek-Brown Constant mi, for Intact Rocks. Engineering Geology, 224, 87–96.
• Yasar, S., 2020. Long Term Wetting Characteristics and Saturation Induced Strength Reduction of Some Igneous Rocks. Environmental Earth Sciences, 79, 14, 353, 1-12.
• Zuo, J. P., Li, H. T., Xie, H. P., Ju, Y., Peng, S. P., 2008. A Nonlinear Strength Criterion for Rock-Like Materials Based on Fracture Mechanics. International Journal of Rock Mechanics and Mining Sciences, 45, 4, 594-599.
• Zuo, J., Shen, J., 2020. The Hoek-Brown Failure Criterion-from Theory to Application. Springer Nature Singapore, 225 s.