Critical Sensitivity and Trans-scale Fluctuations in Catastrophic Rupture

Rupture in heterogeneous brittle media, including earthquakes, can be regarded as complicated phenomena in driven nonlinear threshold systems. It displays catastrophe transition and sample-specificity, which results in difficulty of rupture prediction. Our numerical simulations indicate that critical sensitivity might be a common precursor of catastrophe transition and thus give a clue to catastrophe prediction. In this paper we present an analytical examination of critical sensitivity in driven nonlinear threshold systems, based on mean field approximation and damage relaxation time model. The result suggests that critical sensitivity is in reality a common feature prior to catastrophe transition in driven nonlinear threshold systems, with disordered mesoscopic heterogeneity. This result seems to be supported by rock experiments.

Section: Introductionmentioning

confidence: 99%

Critical Sensitivity in Driven Nonlinear Threshold Systems

张晓晖

许向红

汪海英

et al. 2004

“…Therefore the LURR decreases to a low level before the large event occurs. XIA et al, (2002) presented critical sensitivity to describe the damage evolved in materials. The numerical simulation of the damage and fracture process for brittle inhomogeneous material also shows a peak of sensitivity prior to the catastrophic rupture which is similar to the variation of LURR (ZHANG et al, 2004).…”

Section: Resultsmentioning

confidence: 99%

“…The critical point hypothesis for large earthquakes predicts two different precursory phenomena in space and time, an accelerating moment release and the growth of the spatial correlation length between its different parts. XIA et al (2002) presented critical sensitivity and trans-scale fluctuations associated with catastrophic rupture in a system. Critical sensitivity means that the system becomes significantly sensitive near the catastrophe transition.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emission Experiments of Rock Failure Under Load Simulating the Hypocenter Condition

Zhang

Yin

Liang

et al. 2006

A series of acoustic emission (AE) experiments of rock failure have been conducted under cyclic load in tri-axial stress tests. To simulate the hypocenter condition the specimens are loaded by the combined action of a constant stress, intended to simulate the tectonic loading, and a small sinusoidal disturbance stress, analogous to the Earth tide induced by the Sun and the Moon. Each acoustic emission signal can indicate the occurrence time, location and relative magnitude of the damage (micro-crack) in the specimen. The experimental results verified some precursors such as LURR (Load/Unload Response Ratio) and AER (Accelerating Energy Release) before macro-fracture of the samples. A new parameter, the correlation between the AE and the load, has been proposed to describe the loading history. On the eve of some strong earthquakes the correlation between the Benioff strain and the Coulomb failure stress (CFS) decreases, similar to the variation of LURR prior to strong earthquakes.

“…The catastrophe transition occurring in such media is the most important feature in this problem (BAI et al, 1994;XIA et al, 2002;WEI et al, 2000). In rock mechanics (JAEGER and COOK, 1979), it is found that at the beginning of loading, micro-damages appear on mesoscopic heterogeneities.…”

Section: Introductionmentioning

confidence: 99%

Catastrophic Rupture Induced Damage Coalescence in Heterogeneous Brittle Media

荣峰

汪海英

夏蒙棼

et al. 2006

In heterogeneous brittle media, the evolution of damage is strongly influenced by the multiscale coupling effect. To better understand this effect, we perform a detailed investigation of the damage evolution, with particular attention focused on the catastrophe transition. We use an adaptive multiscale finite-element model (MFEM) to simulate the damage evolution and the catastrophic failure of heterogeneous brittle media. Both plane stress and plane strain cases are investigated for a heterogeneous medium whose initial shear strength follows the Weibull distribution. Damage is induced through the application of the Coulomb failure criterion to each element, and the element mesh is refined where the failure criterion is met. We found that as damage accumulates, there is a stronger and stronger nonlinear increase in stress and the stress redistribution distance. The coupling of the dynamic stress redistribution and the heterogeneity at different scales result in an inverse cascade of damage cluster size, which represents rapid coalescence of damage at the catastrophe transition.