Abstract

The fracture response of geologic materials is of interest for applications, including geothermal energy harnessing and containment of underground explosions. To better understand the explosively induced fracture response of geomaterials, polymethyl methacrylate (PMMA) was used as a transparent rock surrogate to allow imaging of internal shock propagation and fracture growth processes. Experiments were conducted using high-speed shadowgraphy and photon Doppler velocimetry (PDV), which were compared to numerical simulations. Experiments measured fractures produced in 304.8mm × 304.8mm × 304.8mm PMMA cubes with two simultaneously initiated detonators. The cubes were subjected to varying amounts and directions of externally applied uniaxial stresses, including no stress, 2 MPa stress, and 20 MPa stress. The fracture radius as a function of time was extracted from the high-speed videos. Post-test images of the PMMA cubes aided in the determination of three-dimensional effects not directly imaged by the cameras. The surface velocity history and the shock response captured in PDV and the high-speed videos were compared to the simulated explosive-induced shock response. The simulation results indicate that the shock drives the fracture for the first 20 μs corresponding to a fracture radius of approximately 15 mm in the experiments. The gas-driven fracture extent was estimated analytically usingmore » an equilibrium stress distribution calculated after the shock wave propagation through the sample. Reduction in the gas pressure due to the leakage of the explosive products through the crack as a function of time was accounted for. In conclusion, the estimated fracture lengths were in agreement with the experimentally observed fracture lengths.« less

Authors:

Torres, S. M.  ^[1];

• Search DOE PAGES for author "Torres, S. M."
• Search DOE PAGES for ORCID "0009-0002-8717-7206"

Vorobiev, O. Y.  ^[2];

• Search DOE PAGES for author "Vorobiev, O. Y."
• Search DOE PAGES for ORCID "0000-0002-2916-5066"

Robey, R. E. ^[3]; Hargather, M. J.  ^[4]

• Search DOE PAGES for author "Hargather, M. J."
• Search DOE PAGES for ORCID "0000-0001-5861-6770"

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+ Show Author Affiliations

1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); New Mexico Tech, Socorro, NM (United States)
2. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
3. Sandia National Laboratory (SNL-NM), Albuquerque, NM (United States)
4. New Mexico Tech, Socorro, NM (United States)

Publication Date:

Wed Aug 16 00:00:00 EDT 2023

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); US Air Force Office of Scientific Research (AFOSR)

OSTI Identifier:

2007256

Report Number(s):

LLNL-JRNL-852380
Journal ID: ISSN 0021-8979; 1074462

Grant/Contract Number:  

AC52-07NA27344; NA0003988; FA9550-19-1-0379; NA-0003525

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 134; Journal Issue: 7; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

15 GEOTHERMAL ENERGY; Shock waves; Geothermal energy; Optical imaging; Explosives; Polymers; Numerical methods; Heterodyne laser interferometry; Minerals