Mechanical Testing Results on Core from Borehole U-15n, NNSS, in support of SPE

Broome, Scott Thomas; Pfeifle, Thomas W.

doi:10.2172/1488324

Cited by 3 publications

(2 citation statements)

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“…From Vp and Vs, dynamic Young's modulus (E dyn ) and Poisson's ratio (ν dyn ) were calculated. Additional information regarding the material property characterization, including stress‐strain curves, can be found in Broome and Pfeifle (2011), Broome and Lee (2012), and Broome and Lee (2014).…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2020

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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. Here we present material property data: unconfined compressive strength, bulk density (ρ), Young's modulus (E), Poisson's ratio (ν), P wave velocity (V p), and S wave velocity (V s), 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 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.

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Section: Methodsmentioning

confidence: 99%

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

et al. 2020

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“…Specifically, it is assumed that a Coulomb friction law applies on the joint surface to limit the shear stress, such that

T_{s}^{m a x} = T_{coh} + μ_{f} T_{n} .

where T n is the normal stress (positive in compression) applied to the joint's surface and the joint cohesion (

T_{coh} = μ_{f} T_{n}^{\min}

) is determined by the cut‐off value of (

T_{n}^{\min} < 0

) and the friction coefficient μ f . Shear tests performed on core samples of granite from an actual site containing joints show that the friction coefficient μ f is in the range of 0.25 to 0.6. The noncompliant joint model neglects elastic compressibility but allows inelastic sliding with friction.…”

Section: Determination Of the Materials Parametersmentioning

confidence: 99%

A thermomechanical anisotropic continuum model for geological materials with multiple joint sets

Vorobiev

Rubin

2018

Num Anal Meth Geomechanics

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Summary Joints in geological materials introduce elastic compliance and weak planes on which sliding can occur. Although these materials can have multiple joint sets, they often have preferred orientations that cause both elastic and inelastic anisotropic response even when the unjointed material is isotropic. Azimuthal variations in radial velocity and polarity of tangential motion have been observed in experimental data for wave propagation caused by an initially spherical source in a geological material with multiple joint sets. This observed tangential ground motion was found to be related to mechanical anisotropy caused by preferred orientations of joints in the rock. This paper describes thermomechanical continuum constitutive equations, which model the effects of multiple persistent joint sets. A number of quasi‐static examples are considered, which show that the proposed model predicts anisotropic effects of sliding on multiple joint sets similar to those exhibited by computationally expensive mesoscale calculations, which model joint sets explicitly.

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Explosive Yield Estimation Using Regional Seismic Moment Tensors

Ford

Pasyanos

Chiang

2023

Bulletin of the Seismological Society of America

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We use the Pasyanos and Chiang (2022) data set to calculate the seismic moment M0 for each explosion and use the measured explosive yield W to validate the W∼M0 relationship in Denny and Johnson (1991; hereafter, DJ91). The M0 is corrected by transforming to a potency tensor and applying more appropriate near-source geophysical parameter values in the moment estimate. The mean residual between observed and predicted yield is near zero; however, the standard deviation of the residuals results in an F-value (a 95% confidence factor) of about 5. We re-estimate the coefficients in the DJ91 model and find similar values and only a slight improvement in the F-value. Next, we embark on a similar model selection process as DJ91, allowing for non-cube-root yield scaling and other plausible near-source elastic moduli. As was found by DJ91, the yield dependence is not significantly different from unity, and a cube root assumption is valid. Therefore, we yield scale the seismic moment and test the significance of all plausible explanatory variables. Isotropic moment performs better in the response variable than total moment. The preference for isotropic moment could be due to its relationship to volume change, which would be more directly affected by explosive yield. Surprisingly, we find that the overburden pressure, which is a function of depth, is not a significant parameter in the model. We hypothesize that this is due to the competing depth effects on source asymmetry and the incorporation of depth in the Green’s functions used to calculate the seismic moment tensors. Importantly, this emphasizes that only seismic moment tensor-derived moments should be used in these models. After removing insignificant model parameters, we are left with a simple model to predict explosive yield W^ in kt from isotropic moment MI in N·m, W^=κ−1.4132 100.035626GPMI, in which κ and GP are the near-source bulk modulus and gas porosity in Pa and %, respectively. The F-value for this model is approximately 3.

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Mechanical Testing Results on Core from Borehole U-15n, NNSS, in support of SPE

Cited by 3 publications

References 0 publications

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

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

A thermomechanical anisotropic continuum model for geological materials with multiple joint sets

Explosive Yield Estimation Using Regional Seismic Moment Tensors

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