The Use of Rock Mass Classification Systems to Estimate the Modulus and Strength of Jointed Rock

• Published in: Rock mechanics and rock engineering Vol. 43; no. 3; pp. 287 - 304
• Main Authors: Justo, J. L., Justo, E., Azañón, J. M., Durand, P., Morales, A.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.05.2010; Springer; Springer Nature B.V
• Subjects: Applied sciences; Basalt; Buildings. Public works; Civil Engineering; Classification; Earth and Environmental Science; Earth Sciences; Exact sciences and technology; Excavation; Extensometers; Finite element analysis; Geophysics/Geodesy; Geotechnics; Original Paper; Reinforced concrete; Rock deformation; Rocks; Soil investigations. Testing; Soil mechanics. Rocks mechanics; Atlantic Ocean Islands; Canary Islands; Modulus of deformation; Finite elements; Elasto-plastic methods; Rock mass classification; Stability of slopes; Jointed rock; Basalt; Rock mechanics; Site analysis; Deformation modulus; In situ test; Slope stability; Rock mass; Finite element method; Excavating; Elastoplasticity; Classification; Test method; Basalts; Computing method; Strength
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-009-0040-6

Three-dimensional, elastic and elasto-plastic finite element (FE) programs have permitted calculation of the displacements and the factor of safety (FOS) for the excavation for a tower, 132.70 m high (above foundation) on the island of Tenerife. The tower is supported by a 2 m thick reinforced concrete slab on jointed, vesicular and weathered basalt and scoria. The installation of rod extensometers at different depths below the slab has permitted comparison between measured and calculated displacements and the estimation of in situ deformation modulus. The moduli deduced from the simple empirical equations proposed by Hoek et al. (In: NARMS-TAC, 2002 ) and Gokceoglu et al. (Int J Rock Mech Min Sci 40:701–710, 2003 ) as a function of GSI, and Nicholson and Bieniawski (Int J Min Geol Eng 8:181–202, 1990 ) as a function of RMR, provide an acceptable fit with the measured settlements in this type of rock. Good correlation is also obtained with the empirical equation presented by Verman et al. (Rock Mech Rock Eng 30(3):121–127, 1997 ) that incorporates the influence of confining stress in the deformation modulus. The FOS obtained from different correlations with geomechanical classifications is within a relatively narrow range. These results increase our confidence in the use of classification schemes to estimate the deformation and stability in jointed rock.