A New Rock Strength Criterion from Microcracking Mechanisms Which Provides Theoretical Evidence of Hybrid Failure

Abstract

A proper criterion describing when material fails is essential for deep understanding and constitutive modeling of rock damage and failure by microcracking. Physically, such a criterion should be the global effect of local mechanical response and microstructure evolution inside the material. This paper aims at deriving a new mechanisms-based failure criterion for brittle rocks, based on micromechanical unilateral damage-friction coupling analyses rather than on the basic results from the classical linear elastic fracture mechanics. The failure functions respectively describing three failure modes (purely tensile mode, tensile-shear mode as well as compressive-shear mode) are achieved in a unified upscaling framework and illustrated in the Mohr plane and also in the plane of principal stresses. The strength envelope is proved to be continuous and smooth with a compressive to tensile strength ratio dependent on material properties. Comparisons with experimental data are finally carried out. By this work, we also provide a theoretical evidence on the hybrid failure and the smooth transition from tensile failure to compressive-shear failure.

A review of natural hydrofractures in rocks

“…5), although angles of internal friction may vary widely for σ n ≥ 0 (Gudmundsson, 2011). Issues with the transition from hybrid failure to pure shear failure have been discussed by various authors (some examples are Secor, 1965;Phillips, 1972;Engelder, 1999;Ramsey & Chester, 2004;Zhu, 2017), but details of hybrid failure are not the main focus of this paper.…”

A hybrid strength criterion for a soil medium based on tension strength and its implementation in numerical analysis

“…To address these problems, modifications to the tension-shear region have been considered from mathematical methods and experimental methods. For the former, several known curves, such as parabolic curves and hyperbolic curves, are regarded as nonlinear failure envelopes in the tension-shear region (Abbo and Sloan 1995;Singh and Rao 2005a ;Singh and Singh 2005b;Singh et al 2011;You 2009You , 2011Abbo et al 2011;Barsanescu et al 2015;Zhu 2017). This method can be easily implemented in numerical simulations.…”

An experimental study on characterizing damage and fracture of a rock-like material based on three-dimensional magnetic field imaging

“…Researchers around the world have extensively investigated rock fractures and the detection of cracks inside rocks using both mathematical modelling and physical experiments. Zhu (2017) mathematically analyzed various modes of fractures based on a fracture criterion for brittle rocks and redefined the crack tensor using the normalization approach, based on which they described the crack distribution characteristics relatively well. Fathi et al (2016) proposed a new method for characterizing fracture toughness.…”