The effect of anisotropy on the mechanical properties of artificial rock mass based on laboratory physical modelling

Lohrasb Faramarzi¹ , Mohammad Darbor² , Behnam Ebrahimi Jouzdani³ , Seyed Hadi Hoseinie⁴

¹ Dept. of Mining Engineering, Isfahan University of Technology. Isfahan. Iran

² Mining Engineering Faculty, Sahand University of Technology

³ Laboratory of Concrete and Building Materials, Department of Civil Engineering, Isfahan University of Technology, Isfahan, Iran

⁴ Dept. of Mining Engineering, Isfahan University of Technology. Isfahan. Iran

Doi:10.22034/ANM.2022.2860

Abstract

Assessment of strength anisotropy has been one of the most challenging subjects in rock mechanics and civil engineering. The orientation of the discontinuity plane, the aggregate distribution, and the specimen size have a significant influence on the mechanical properties of rock and cementitious materials. This study aims to evaluate the effect of anisotropy on uniaxial compressive strength, elastic constants, and destruction-specific energy using physical modelling. For this purpose, different concrete blocks were produced in which aggregate sizes of 9.5, 12.5, and 19 mm were used. Different cylindrical specimens with diameters of 45, 69, and 94 mm were prepared. A suite of laboratory testing was performed on prepared concrete samples as a function of discontinuity plane angle (α=30°,45°, and 60°), including uniaxial compressive strength and deformability tests. The results obtained have shown that the mechanical properties of cementitious materials have different values concerning the banding plane, aggregate size, and specimen volume. It was shown that the uniaxial compressive strength and tangent modulus of elasticity shows the highest values in low discontinuity plane angle than those obtained in the other directions. However, in concrete mixtures with a grain size of 0-19 mm, an increasing-decreasing trend of strength behavior was observed with ascending the orientation of the discontinuity plane from 30° to 60°. The findings presented indicated that with increasing aggregate size, strength properties descend due to rise heterogeneities that affect failure modes. Finally, it was revealed that when specimen size increases from 69 to 94 mm in diameter, led to significant rises in the values of compressive strength and elasticity modulus in cementitious materials.

Keywords: Anisotropy, Grain size, Specimen size, Mechanical properties, Destruction specific energy, Physical modelling