Bearing of Structural Anisotropy on Deformation and Mechanical Response of Rocks: An Experimental Example of Rocksalt Deformation Under Variable Compression Rates

Abstract

ABSTRACT The deformation and mechanical responses of rocks are prime concern in development of varieties of civil and mining engineering structures. The deformation and mechanical properties of both natural and artificial materials are strongly depend on mineral constituents and their arrangements, temperatures and pressures, stress rates and structural anisotropy. This study elaborates an understanding of structural anisotropy, compression rates and mechanical attributes relationship in rocks with specific examples of deformed rocksalt. The cubical samples (5X5X5 cm3) with three kinds of structural anisotropy were subjected to quasistatic compressive stress at rates 0.00035 MPa/min, 0.0035 MPa/min, 0.035 MPa/min, 0.35 MPa/min, 3.5MPa/min, 5 MPa/min, 7MPa/min and 9 MPa/min on servo-controlled Material Testing System (MTS). The stress-strain curves prepared from deformation of rocksalt’s samples under different rates of compressions are used to determine major mechanical parameters viz., strengths, strains, and modulus of elasticity. A micro-mechanical en-echelon crack array model is proposed to explain the influence of structural anisotropy on deformation patterns and mechanical properties of rocksalt. According to the proposed model the deformation progresses due to different proportional contributions of tensile and shear crack arrays under the influence of structural anisotropy. The control of structural anisotropy loses with respect to increment in rate of compression with enhance contribution of shear crack arrays in comparison to tensile crack arrays and ultimately fails in shear where the structurally anisotropic rock show isotropic behaviour.