Strength and ductility of room-dry and water-saturated igneous rocks at low pressures and temperatures to partial melting. Final report

Friedman, M.; Handin, John; Higgs, N. G.; Lantz, J.R.; Bauer, S. J.

doi:10.2172/6919451

Cited by 17 publications

(14 citation statements)

References 12 publications

(15 reference statements)

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“…Confinement, initial grain size, strain rate, and cyclic loading certainly play important roles, which need to be thoroughly investigated. Nevertheless, our results, like that of Friedman et al [], suggest that, under confinement (here 30 MPa, 50 MPa in the case of Friedman et al []), the peak strength of fine grain‐size crystalline rocks are actually quite insensitive to initial damage. An unanswered question then remains: How high is the pressure required to negate the effect of thermal cracking?…”

Section: Discussionsupporting

confidence: 77%

“…Many studies have concentrated on the effect of crack damage on elastic and transport properties, often by using thermally cracked material [ Fredrich and Wong , ; Darot and Reuschlé , ; Vinciguerra et al , ; Nara et al , ; Ougier‐Simonin et al , , ; Wang et al , ; Faoro et al , ]. Some years ago, Friedman et al [] heated Charcoal granodiorite to 1000°C, and then deformed the thermally cracked samples at confining pressure of 50 MPa, which turned out to be as strong as an unheated sample deformed at the same pressure. Similar behavior was observed in Cuerbio basalt heated to 750°C.…”

Section: Introductionmentioning

confidence: 99%

“…Similar behavior was observed in Cuerbio basalt heated to 750°C. However, Friedman et al [] also observed that in unconfined experiments, the uniaxial compressive strengths (UCS) of thermally cracked granodiorite samples could be reduced by as much as a factor of 4 compared to that of the unheated samples. Many studies on UCS of rock as function of temperature confirm this overall weakening trend related to thermal cracking on brittle strength in the absence of confinement.…”

Section: Introductionmentioning

confidence: 99%

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Physical properties and brittle strength of thermally cracked granite under confinement

et al. 2013

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[1] Effects of thermal crack damage on the rupture processes of a fine-grained granite were investigated under triaxial stress, under water (wet) and argon gas (dry) saturated conditions, and at room temperature. Thermal cracking was introduced by slowly heating and cooling two samples of La Peyratte granite up to 700 ı C, which were compared to two intact specimens. For each rock sample, a hydrostatic test was first carried up to 90 MPa effective pressure (5 MPa constant pore pressure). The samples were then deformed to failure at a constant strain rate of 2.10 -6 s -1 , at 30 MPa effective pressure. Our results show that (1) permeability of heat-treated specimens was 4-5 orders of magnitude larger than that of intact specimens at low effective mean pressure; (2) nevertheless, at our experimental conditions (2.10 -6 s -1 ), thermal cracking had no significant influence on the brittle strength; (3) similarly, no obvious water weakening effect was observed; (4) however, with increasing stress, elastic anisotropy appeared at lower differential stress in heat-treated specimens than in intact ones, but close to failure, the magnitude of P wave anisotropy was approximately the same for both types of specimens; (5) acoustic emission hypocenter locations and P wave velocity anisotropy in the basal plane demonstrate that strain localization started right at the onset of dilatancy for heat-treated specimens, later in the intact specimens; and (6) inverting wave velocities for crack density, we show that failure was reached for vertical crack densities of 0.35 for dry specimens and possibly 0.5 for water-saturated specimens.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Physical properties and brittle strength of thermally cracked granite under confinement

et al. 2013

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“…This analysis indicates that Φ → 0 o as pressure increases to 800 bar and c increases substantially with increase in pressure and can be as high as 340 MPa at 800 MPa for Carrara marble. Increases in temperature suggest also that Φ → 0 o as temperature increases (Friedman et al., ) although the data are meagre. Thus, the assumptions of Yamato and Brun () for values of the constitutive parameters are unsubstantiated and do not make physical sense as c = 0 represents a cohesionless sand and Φ = 30 o represents a very high pressure dependence that is not reflected in the experimental stress strain curves at high pressures.…”

Section: Two Examplesmentioning

confidence: 99%

Pressure and equilibrium in deforming rocks

Hobbs

Ord

2017

Journal Metamorphic Geology

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It is widely proposed that tectonic pressure (the difference between the mean stress and the pressure arising from a lithostatic load) is large, and has a significant influence on mineral phase equilibria in deforming metamorphic rocks. The implication/assertion is that the mean stress is equivalent to the thermodynamic pressure which characterizes mineral phase equilibria and is a measure of how the energy changes as the volume changes. We distinguish two useful thermodynamic pressures. The first is an equilibrium thermodynamic pressure, characteristic of non‐dissipative systems and related directly to equilibrium values of the chemical potentials that define stable, equilibrium phase assemblages. The second is a non‐equilibrium thermodynamic pressure characteristic of dissipative systems with zero net entropy production and related to non‐equilibrium chemical potentials that define stable non‐equilibrium phase assemblages. In many dissipative metamorphic systems discussed in the literature, the concepts of thermodynamic pressure and chemical potential are not usefully defined because the system is not at equilibrium and/or no volume change is involved in the deformation. The conclusion of this note is that the influence of tectonic pressure on phase equilibria is minor. The role of tectonic pressure is an important issue but is only relevant to phase equilibrium when an equilibrium thermodynamic pressure can be defined; in such cases, the influence of tectonic pressure is small compared to many proposals in the literature. Except for elastic deformations, the mean stress is not useful in discussing mineral phase equilibrium.

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“…This can take place at temperatures as low as 300˚ C. On further heating, the elastic properties of the rock change considerably, permitting disintegration under lower levels of applied stress than would otherwise be the case. For example, in laboratory tests, Friedman et al (3) observed the ultimate strength of an unconfined sample of granodiorite to decrease from 360 MPa (52,500 psi) at 25˚ C to 30 MPa (4,350 psi) at 1,000˚ C. Similarly, porous and fractured rocks display a roughly fourfold reduction of strength when heated.…”

Section: The Spallation Processmentioning

confidence: 99%

The Hydratherm Hybrid Drilling Systems For Cheaper Heavy Oil Recovery

North

Knibb

Ali

2001

Journal of Canadian Petroleum Technology

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Nearly 20 years of research and field testing has resulted in the development of Hydratherm™'s hybrid drilling system, which uses ultra-high pressure (UHP) drilling fluid jets and/or a variable thermal spallation gas jet. The gas jet subjects the host rock to pulsed heat fluxes at temperatures ranging from 200˚ C to 1,100˚ C, producing thermal expansion and strength reduction of the rock-forming minerals. The UHP jets then quench, cut and erode the rock momentarily after heating. The combined mechanisms enable ultra-fast rock penetration (20 -50 m/hr in hard rock) by means of spallation, erosion, fracturing, chipping and cutting.This technology should bring about exciting developments in heavy oil recovery, tar sand and oil shale exploitation, as well as having wider applications in mining, tunnelling and geothermal energy recovery ("HDR heat mining").

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Strength and ductility of room-dry and water-saturated igneous rocks at low pressures and temperatures to partial melting. Final report

Cited by 17 publications

References 12 publications

Physical properties and brittle strength of thermally cracked granite under confinement

Physical properties and brittle strength of thermally cracked granite under confinement

Pressure and equilibrium in deforming rocks

The Hydratherm Hybrid Drilling Systems For Cheaper Heavy Oil Recovery

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