Modelling the time-dependent rheological behaviour of heterogeneous brittle rocks

Abstract

International audienceA 2-D numerical model for brittle creep and stress relaxation is proposed for the timedependent brittle deformation of heterogeneous brittle rock under uniaxial loading conditions. The model accounts for material heterogeneity through a stochastic local failure stress field, and local material degradation using an exponential material softening law. Importantly, the model introduces the concept of a mesoscopic renormalization to capture the co operative interaction between microcracks in the transition from distributed to localized damage. The model also describes the temporal and spatial evolution of acoustic emissions, including their size (energy released), in the medium during the progressive damage process. The model is first validated using previously published experimental data and is then used to simulate brittle creep and stress relaxation experiments. The model accurately reproduces the classic trimodal behaviour (primary, secondary and tertiary creep) seen in laboratory brittle creep (constant stress) experiments and the decelerating stress during laboratory stress relaxation (constant strain) experiments. Brittle creep simulations also show evidence of a 'critical level of damage' before the onset of tertiary creep and the initial stages of localization can be seen as early as the start of the secondary creep phase, both of which have been previously observed in experiments. Stress relaxation simulations demonstrate that the total amount of stress relaxation increases when the level of constant axial strain increases, also corroborating with previously published experimental data. Our approach differs from previously adopted macroscopic approaches, based on constitutive laws, and microscopic approaches that focus on fracture propagation. The model shows that complex macroscopic time-dependent behaviour can be explained by the small-scale interaction of elements and material degradation. The fact that the simulations are able to capture a similar time-dependent response of heterogeneous brittle rocks to that seen in the laboratory implies that the model is appropriate to investigate the non-linear complicated time dependent behaviour of heterogeneous brittle rocks

Microseismic monitoring and stability evaluation for the large scale underground caverns at the Houziyan hydropower station in Southwest China

“…The maximum tensile strain criterion and the modified Mohr-Coulomb criterion with a tension cutoff were used as two damage thresholds in the damage mechanics-based model (Jeager et al, 2007). Additional details regarding the application and description of the RFPA code can be found in Tang et al (1998) and in other literatures Xu et al, 2012bXu et al, , 2014bWang et al, 2013;Wei et al, 2014;Li et al, 2006).…”

Influence of the geometry of partially-spanning joints on mechanical properties of rock in uniaxial compression

“…According to the definition, a larger m implies a more homogeneous material and vice versa. More details about the application and description of the numerical model can be found in Tang et al (2008), Tang et al (2006), and Xu et al (2012).…”

Fracture mechanical behavior of red sandstone containing a single fissure and two parallel fissures after exposure to different high temperature treatments

“…In the past, the strength, deformation, failure and time-dependent behavior of sandstone have been reported in a number of experimental studies (Wu et al, 2007;Klein et al, 2001;B esuelle et al, 2003;Feng et al, 2004;Fortin et al, 2006;Tembe et al, 2008;Tsai et al, 2008;Yang et al, 2008;Heap et al, 2009b;Park and Bobet, 2009;Tavallali and Vervoort, 2010;Heap et al, 2010;Xu et al, 2012;Song et al, 2013;Wasantha and Ranjith, 2014;Yang et al, 2014b). For example, Khan et al (1991) conducted a lot of triaxial compression experiments on Berea sandstone under a large range of confining pressure, determined the initial yield and failure surfaces, and proposed a yield and failure criteria.…”