Fracture propagation in Indiana Limestone interpreted via linear softening cohesive fracture model
- New Mexico Tech, Socorro, NM (United States). Earth and Environmental Science Dept.; Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.; New Mexico Tech, Socorro, NM (United States). New Mexico Bureau of Geology
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Solid Mechanics Dept.
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.
Abstract We examine the use of a linear softening cohesive fracture model (LCFM) to predict single‐trace fracture growth in short‐rod (SR) and notched 3‐point‐bend (N3PB) test configurations in Indiana Limestone. The broad goal of this work is to (a) understand the underlying assumptions of LCFM and (b) use experimental similarities and deviations from the LCFM to understand the role of loading paths of tensile fracture propagation. Cohesive fracture models are being applied in prediction of structural and subsurface fracture propagation in geomaterials. They lump the inelastic processes occurring during fracture propagation into a thin zone between elastic subdomains. LCFM assumes that the cohesive zone initially deforms elastically to a maximum tensile stress ( σ max ) and then softens linearly from the crack opening width at σ max to zero stress at a critical crack opening width w 1 . Using commercial finite element software, we developed LCFMs for the SR and N3PB configurations. After fixing σ max with results from cylinder splitting tests and finding an initial Young's modulus ( E ) with unconfined compressive strength tests, we manually calibrate E and w 1 in the SR model against an envelope of experimental data. We apply the calibrated LCFM parameters in the N3PB geometry and compare the model against an envelope of N3PB experiments. For accurate simulation of fracture propagation, simulated off‐crack stresses are high enough to require inclusion of damage. Different elastic moduli are needed in tension and compression. We hypothesize that the timing and location of shear versus extensional micromechanical failures control the qualitative macroscopic force‐versus‐displacement response in different tests. For accurate prediction, the LCFM requires a constant style of failure, which the SR configuration maintains until very late in deformation. The N3PB configuration does not maintain this constancy. To be broadly applicable between geometries and failure styles, the LCFM would require additional physics, possibly including elastoplastic damage in the bulk material and more complicated cohesive softening models.
- Research Organization:
- Energy Frontier Research Centers (EFRC), Washington D.C. (United States). Center for Frontiers of Subsurface Energy Security (CFSES)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0001114; AC04-94AL85000
- OSTI ID:
- 1370735
- Alternate ID(s):
- OSTI ID: 1402255
- Journal Information:
- Journal of Geophysical Research. Solid Earth, Vol. 120, Issue 4; Related Information: CFSES partners with University of Texas at Austin (lead); Sandia National Laboratory; ISSN 2169-9313
- Publisher:
- American Geophysical UnionCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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