Relationship between strain localization and catastrophic rupture

Abstract

In order to explore a prior warning to catastrophic rupture of heterogeneous media, like rocks, the present study investigates the relationship between surface strain localization and catastrophic rupture. Instrumented observations on the evolution of surface strain field and the catastrophic rupture of a rock under uniaxial compression were carried out. It is found that the evolution of surface strain field displays two phases: at the early stage, the strain field keeps nearly uniform with weak fluctuations increasing slowly; but at the stage prior to catastrophic rupture, a certain accelerating localization develops and a localized zone emerges. Based on the measurements, an analysis was performed with local mean-field approximation. More importantly, it is found that the scale of localized zone is closely related to the catastrophic rupture strain and the rupture strain can be calculated in accord with the local-mean-field model satisfactorily. This provides a possible clue to the forecast of catastrophic rupture.

Power-law singularity as a possible catastrophe warning observed in rock experiments

“…As shown in some theories in rock mechanics, there would be no catastrophic rupture under absolutely stiff loading. In fact, under certain conditions, catastrophic rupture may be triggered by damage localization even in an absolutely stiff testing machine [42][43][44][45]. However, it should be noted that the testing apparatus used in the experiments is elastic (to simulate most practical cases) with a stiffness of about 60 kN/mm, which is about 1/10 of the intact sample stiffness; thus, catastrophic rupture appears under certain conditions.…”

Scaling law of average failure rate and steady-state rate in rocks

“…This leads to an effect of strain hardening in the type 1 (Hao et al 2013) and type 2 experiments (Lockner and Byerlee 1980;Lockner 1993). The secondary stage corresponds to the stage where damage to rock samples occurs randomly, and thus the spatial distribution of the strain field presents weak fluctuations (Hao et al 2007(Hao et al , 2010. This occurs so that the macroscopic physical quantities (e.g., average strain or stress) that describe the global average mechanical responses evolve steadily.…”

“…The solid blue line plots the axial deformation (u) against time, and the solid red squares plot the stress-time curve. It can be seen that at the early stage, the stress-time curve is slightly convex upwards (also see Rudnicki and Rice 1975;Jeager et al 2007;Hao et al 2007Hao et al , 2013 and the deformation growth is characterized by an initial convex upward phase of decreasing strain rate. Later, an almost linear stress-time relation, as well as a nearly linear u * t relation, follows.…”

“…3). It has been demonstrated that the catastrophic failure is induced by the elastic energy release from the loading apparatus, which occurs at some point in the strain softening section after peak stress (Salamon 1970;Hundson et al 1972;Labuz and Biolzi 1991;Bai et al 2005;Jeager et al 2007;Hao et al 2007Hao et al , 2010Hao et al , 2013. Figure 6 plots the deformation-displacement curves for specimens.…”

Application of DICM on Similar Material Simulation Experiment for Rock-Like Materials

“…Zhao et al [4] used the DIC technique to test the deformation field of the rock material plate with the size of 25 × 13 × 1.1 mm containing microcracks and found that the deformation varied in different areas separated by subcracks, which implied the effect of crack opening and closing in rock. Hao et al [5,6] described the deformation localization during the fracturing process of rock material specimens with the dimensions of 20 × 16 × 40 mm based on DIC and found that the size of the localized zone decreased from the sample size at peak load to an eventual value. Yang et al [7] and Yang and Jing [8] analyzed the fracture coalescence behavior of rock, tested rectangular prismatic sandstone specimens with the dimensions of 80 × 160 × 30 mm, containing three fissures under uniaxial compression, and discussed the strain field evolution and law of crack propagation by DIC.…”