Universität zu Köln

Kun, Ferenc ORCID: 0000-0001-6469-7917, Varga, Imre, Lennartz-Sassinek, Sabine and Main, Ian G. (2013). Approach to failure in porous granular materials under compression. Phys. Rev. E, 88 (6). COLLEGE PK: AMER PHYSICAL SOC. ISSN 1550-2376

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Abstract

We investigate the approach to catastrophic failure in a model porous granular material undergoing uniaxial compression. A discrete element computational model is used to simulate both the microstructure of the material and the complex dynamics and feedbacks involved in local fracturing and the production of crackling noise. Under strain-controlled loading, microcracks initially nucleate in an uncorrelated way all over the sample. As loading proceeds the damage localizes into a narrow damage band inclined at 30 degrees-45 degrees to the load direction. Inside the damage band the material is crushed into a poorly sorted mixture of mainly fine powder hosting some larger fragments. The mass probability density distribution of particles in the damage zone is a power law of exponent 2.1, similar to a value of 1.87 inferred from observations of the length distribution of wear products (gouge) in natural and laboratory faults. Dynamic bursts of radiated energy, analogous to acoustic emissions observed in laboratory experiments on porous sedimentary rocks, are identified as correlated trails or cascades of local ruptures that emerge from the stress redistribution process. As the system approaches macroscopic failure consecutive bursts become progressively more correlated. Their size distribution is also a power law, with an equivalent Gutenberg-Richter b value of 1.22 averaged over the whole test, ranging from 3 to 0.5 at the time of failure, all similar to those observed in laboratory tests on granular sandstone samples. The formation of the damage band itself is marked by a decrease in the average distance between consecutive bursts and an emergent power-law correlation integral of event locations with a correlation dimension of 2.55, also similar to those observed in the laboratory (between 2.75 and 2.25).

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Kun, Ferenc UNSPECIFIED orcid.org/0000-0001-6469-7917 UNSPECIFIED Varga, Imre UNSPECIFIED UNSPECIFIED UNSPECIFIED Lennartz-Sassinek, Sabine UNSPECIFIED UNSPECIFIED UNSPECIFIED Main, Ian G. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-469923
DOI:	10.1103/PhysRevE.88.062207
Journal or Publication Title:	Phys. Rev. E
Volume:	88
Number:	6
Date:	2013
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	1550-2376
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language DEFORMATION; GROWTH; MODEL; EVOLUTION; RUPTURE; GOUGE Multiple languages Physics, Fluids & Plasmas; Physics, Mathematical Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/46992