The effect of cracks on the uniaxial elastic compression of rocks

Walsh, J. B.

doi:10.1029/jz070i002p00399

Cited by 565 publications

(209 citation statements)

References 10 publications

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“…Walsh, in a recent paper, shows that Young's modulus for an elastic solid containing cracks is less than that for an identical solid without cracks (Ref. 35). This is an excellent corroboration of the interpretation NAvm~1ps RrFpORT 8'r34 presented that relies upon grain-to-grain cracking and bond damage as the cause of lessened strength and modulus upon stress wave transit.…”

Section: Diorite the Results Of Experiments On Diorite Presented Havsupporting

confidence: 54%

Stress Wave Passage in Selected Rock Fabrics

Austin¹,

Goldsmith²,

Finnegan³

1965

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P'AVWEPSABSTRACT. This study is on the transmission and decay of pulses produced by impact in a very coarse-grained leucogranite, a fine-grained spessartite, and a fine-grained to aphanitic basalt. For most tests, ballistically suspended Hopkinson bars of these rock materials, 0.845 inches in diameter and 18 inches long, were subjected to longitudinal impact by i-inch-diameter hardened steel spheres at an initial velocity of 3,250 + 1.5% ips. Strain gages attached to the specimens at variLtas stations recorded the shape and velocity of propagation of the resultant wave in the rock rod. Similar experiments were performed on an aluminum alloy rod of identical size to assess the magnitude of the dispersion resulting from the three-dimensional character of the rod. The nature of the pulse transformation during passage permits an assessment of the validity of various models proposed for geologic substances in the field of seismology. Static tests on virgin and shocked rods were generally found to agree with predicted effects of stress wave passage on the rock structure.These effects include compressive-strength loss in the impact end and tensile-strength loss in the distal end as the result of oriented fractures and a general lowering of the static Young's modulus.Although these studies were conducted on rock, the general concepts developed are fully applicable to an understanding of the dynamic behavior of artificial granular brittle solids, such as explosives and concrete.

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Section: Diorite the Results Of Experiments On Diorite Presented Havsupporting

confidence: 54%

Stress Wave Passage in Selected Rock Fabrics

Austin¹,

Goldsmith²,

Finnegan³

1965

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“…13 and 14) may have weakened the rock and localized bending strains. Previous studies have demonstrated quantitatively how joints may act to increase the compliance of an elastic material and accommodate inelastic strains (Segall, 1984;Walsh, 1965). Layer-parallel slip may also reduce fold wavelength by reducing the effective elastic thickness of the folding layer.…”

Section: Discussion Of Model Resultsmentioning

confidence: 99%

Deformation associated with a continental normal fault system, western Grand Canyon, Arizona

Resor

2008

Geological Society of America Bulletin

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Reverse-drag folds are often used to infer subsurface fault geometry in extended terrains, yet details of how these folds form in association with slip on normal fault systems are poorly understood. Detailed structural mapping and global positioning system (GPS) surveying of the Frog Fault and Lone Mountain Monocline in the western Grand Canyon demonstrate a systematic relationship between elements of the normal fault system and fold geometry. The Lone Mountain Monocline, which parallels the Frog Fault, is made up of two half-monoclinal fl exures: a hanging-wall fold in which dips gradually increase toward the fault over ~1.5 km reaching a maximum dip of 25° and a footwall fold in which dips decrease away from the fault over ~0.5 km from a maximum of 12°. The highest dips associated with folding are found where throw on the Frog Fault and a synthetic fault are at a maximum. Lower dips are found where there is less throw on the Frog Fault and antithetic faults are present. This relationship between fault and fold geometry suggests that the folding is associated with Basin and Range extension rather than Laramide contraction. Mechanical models of normal faultrelated deformation predict similar patterns of folding over planar faults of fi nite extent and corroborate the important role of subsidiary fault geometry in the overall pattern of deformation. Application of these models in an inverse sense yields ~1 km estimates of down-dip extent, a result that may indicate fault confi nement within the sedimentary section or weakening effects associated with folding layered strata. A general analysis illustrates that reverse-drag folds of moderate dip are expected to form in association with slip on planar faults of fi nite extent-a result that has the potential to impact our estimates of hydrocarbon volumes, crustal extension, and earthquake hazards associated with continental normal faults.

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“…8) is of the type commonly observed in uniaxial loaded, fractured rocks (i.e. irreversible, but closely recoverable -David et al, 2012;Jaeger et al, 2007;Walsh, 1965), but also in the case of isostatic loading of anisotropic rocks (see Skurtveit et al, 2012 for a North Sea shale sample exposed to brine). Furthermore, a comparison of the magnitude of apparent bulk moduli obtained here with the bulk moduli obtained through ultrasonic velocity measurements (Morcote et al, 2010;Schuyer et al, 1954) yield relatively low values both in the evacuated and fluid-equilibrated states.…”

Section: Strain Recoverability Prosper Haniel Coalmentioning

confidence: 99%

Sorption and changes in bulk modulus of coal — experimental evidence and governing mechanisms for CBM and ECBM applications

Hol

Gensterblum

Massarotto

2014

International Journal of Coal Geology

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Recent studies report that the stiffness of coal changes, when exposed to sorbing gases such as CH 4 and CO 2 . Although this effect might be potentially important for predicting the in situ mechanical behavior of coal seams during CH 4 production or CO 2 sequestration, very little understanding exists on the underlying mechanisms. In this paper, we report a single, long-duration mechanical test on a large, cube-shaped coal sample (Ruhr Basin, Germany). The sample was subjected to isostatic loading and unloading; first in the evacuated state (as received), and then each time after exposing it to pressurized, non-adsorbing He, or sorbing N 2 , CH 4 , and CO 2 . We find that exposure to sorbing gases led to swelling, which introduced a hysteresis in the stress-strain trajectory followed during mechanical loading. This hysteresis was almost absent in the evacuated state, and its magnitude depended strongly on the amount of adsorption-induced swelling exhibited by the sample. The apparent bulk modulus determined here for the CO 2 -equilibrated state was approximately 25% lower compared to the evacuated state. We qualitatively consider mechanisms that affect the elastic behavior of coal at the matrix and bulk scale, and argue that the observed effects are a combined effect of 1) changes in surface roughness at cleat interfaces and microfractures, and 2) a thermodynamic coupling between stress state, sorption capacity and swelling strain. The changes in stiffness relate to fluid-rock interaction effects, as well as to the presence of fractures, and hence not to the inherent elastic properties of the solid phase itself. We discuss the characteristics of each mechanism and the connection of the proposed mechanisms with formation-scale geomechanical effects of coal layers under conditions relevant to CBM/ECBM.

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The effect of cracks on the uniaxial elastic compression of rocks

Cited by 565 publications

References 10 publications

Stress Wave Passage in Selected Rock Fabrics

Stress Wave Passage in Selected Rock Fabrics

Deformation associated with a continental normal fault system, western Grand Canyon, Arizona

Sorption and changes in bulk modulus of coal — experimental evidence and governing mechanisms for CBM and ECBM applications

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