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The Complicated Link Between Material Properties and Microfracture Density for an Underground Explosion in Granite

Journal Article · · Journal of Geophysical Research. Solid Earth
DOI:https://doi.org/10.1029/2020JB019894· OSTI ID:1708923
 [1];  [2];  [3];  [2]
  1. Los Alamos National Laboratory Los Alamos NM USA
  2. Los Alamos National Laboratory Los Alamos NM USA, Sandia National Laboratories Albuquerque NM USA
  3. Sandia National Laboratories Albuquerque NM USA

Geophysical techniques are often implemented as quick and inexpensive ways to locate and characterize fractures in the subsurface, which is important for a number of geoscience fields. Seismic velocities are the most widely used proxies for identification of fractures, but the correlation is not always well-defined. In this study we present material property data: unconfined compressive strength (UCS), bulk density (ρ), Young's modulus (E), Poisson's ratio (ν), P wave velocity (Vp), and S wave velocity (Vs), in conjunction with microfracture densities measured on samples of granite collected before and after underground chemical explosions. Results indicate the relationship between fractures and material properties is complex, even in this single-lithology environment. We interpret that this complexity arises from varying fracture mechanisms (e.g. dilation-inducing fractures vs compression-inducing fractures) in different parts of the core, due to differences in stress conditions. Additional complexity may result from chemical interactions between the fresh fractures and the fluids in the area. Water content appears to have a significant, if not dominant, role in the unconfined compressive strength (UCS) of the samples. We suggest caution when using elastic property measurements as a proxy for fracturing in areas of explosion-induced damage, or in other areas where a variety of mechanisms induce fracturing.

Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
Grant/Contract Number:
AC04-94AL85000; NA0003525; AC52-06NA25946
OSTI ID:
1708923
Alternate ID(s):
OSTI ID: 1721597
OSTI ID: 1786777
OSTI ID: 3009682
OSTI ID: 1699477
OSTI ID: 1429706
Journal Information:
Journal of Geophysical Research. Solid Earth, Journal Name: Journal of Geophysical Research. Solid Earth Journal Issue: 11 Vol. 125; ISSN 2169-9313
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English

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