Compression Wave Velocity of Cylindrical Rock Specimens: Engineering Modulus Interpretation

Cha, Min-Seok; Cho, Gye-Chun

doi:10.1143/jjap.46.4497

Cited by 15 publications

(9 citation statements)

References 3 publications

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“…The attenuation of a rock specimen was obtained by a free-free resonant column (FFRC) test (Vaghela and Stokoe 1995;Kim et al 1997;Cha and Cho 2007). The FFRC method measures the attenuation of the longitudinal wave mode (i.e., also called as rod wave or bar wave).…”

Section: Free-free Resonant Column Testmentioning

confidence: 99%

“…We subsequently subjected the saturated specimens to a drying process in an oven and repeated the same elastic wave and mass measurement procedure. /Q max -1 ) with respect to a range of the permeabilities and pore sizes when the porosity n = 2.6%, Young's modulus E = 45 GPa, frequency f = 23 kHz, and Poisson's ratio m = 0.24 a Rod-wave velocity of a dry specimen at the resonance frequency was determined by using a free-free resonant column (FFRC) method (Vaghela and Stokoe 1995;Kim et al 1997;Cha and Cho 2007) b P-wave velocity of a dry specimen was determined by using the pointsource travel time method (Cha and Cho 2007) c Young's modulus (i.e., E = qV P 2 ) was calculated by using the dry density and the P-wave velocity of a specimen at a dry condition d Poisson's ratio is calculated by using the P-wave velocity and rod-wave velocity of a specimen at a dry condition…”

Section: Free-free Resonant Column Testmentioning

confidence: 99%

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Effect of Partial Water Saturation on Attenuation Characteristics of Low Porosity Rocks

Kwon

Cho

2010

Rock Mech Rock Eng

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Section: Free-free Resonant Column Testmentioning

confidence: 99%

Section: Free-free Resonant Column Testmentioning

confidence: 99%

Effect of Partial Water Saturation on Attenuation Characteristics of Low Porosity Rocks

Kwon

Cho

2010

Rock Mech Rock Eng

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“…Figure 1 shows the variations of P-waves with Poisson's ratio for elastic homogeneous and isotropic media. Given Poisson's ratio, P-wave velocity is in a range between unconstrained and constrained velocities [13]. P-wave velocity increases with increasing the degree of confinement, and the confinement effect increases as Poisson's ratio increases.…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Dynamic Elastic Modulus of Concrete Using Shear-Wave Velocity Measurements

Lee¹,

Kee

et al. 2017

Advances in Materials Science and Engineering

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The objectives of this study are to investigate the relationship between static and dynamic elastic moduli determined using shear-wave velocity measurements and to demonstrate the practical potential of the shear-wave velocity method for in situ dynamic modulus evaluation. Three hundred 150 by 300 mm concrete cylinders were prepared from three different mixtures with target compressive strengths of 30, 35, and 40 MPa. Static and dynamic tests were performed at 4, 7, 14, and 28 days to evaluate the compressive strength and the static and dynamic moduli of the cylinders. The results obtained from the shear-wave velocity measurements were compared with dynamic moduli obtained from standard test methods (P-wave velocity measurements according to ASTM C597/C597M-16 and fundamental longitudinal and transverse resonance tests according to ASTM C215-14). The shear-wave velocity measured from cylinders showed excellent repeatability with a coefficient of variation (COV) less than 1%, which is as good as that of the standard test methods. The relationship between the dynamic elastic modulus based on shearwave velocity and the chord elastic modulus according to ASTM C469/C469M was established. Furthermore, the best-fit line for the shear-wave velocity was also demonstrated to be effective for estimating compressive strength using an empirical relationship between compressive strength and static elastic modulus.

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“…Porosity and permeability were measured using a CMS 300 automated permeameter (CoreLab). Dynamic elastic constants were calculated from densities and acoustic wave velocities (Cha and Cho 2007). Static Young's 1 2 3 4 5 6 7 8 9 modulus, unconfined uniaxial compressive strength, and splitting tensile strength were measured according to the ASTM standards (ASTM 2008(ASTM , 2014b.…”

Section: Intact Rock Propertiesmentioning

confidence: 99%

Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation

et al. 2018

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A laboratory study of cryogenic fracturing was performed to test its ability to improve oil/gas recovery from low-permeability reservoirs. Our objective is to develop well-stimulation technologies using cryogenic fluids, e.g. liquid nitrogen (LN) to increase permeability in a large reservoir volume surrounding wells. The new technology has the potential to reduce formation damage caused by current stimulation methods as well as minimize or eliminate water usage. The concept of cryogenic fracturing is that sharp thermal gradient (thermal shock) created at the surfaces of formation rocks by applying cryogenic fluid can cause strong local tensile stress and initiate fractures. We developed a laboratory system for cryogenic fracturing under true-triaxial loading, with liquid nitrogen delivery/control and measurement systems. The loading system simulates confining stresses by independently loading each axis up to about 5000 psi on 8"×8"×8" cubes. Both temperature in boreholes and block surfaces and fluid pressure in boreholes were continuously monitored. Acoustic and pressure-decay measurements were obtained before and at various stages of stimulations. Cubic blocks (8"×8"×8") of Niobrara shale, concrete, and sandstones were tested, and stress levels and anisotropies varied. Three schemes were considered: gas fracturing without cryo-stimulation, gas fracturing after low-pressure cryogen flowthrough, and gas fracturing after high-pressure cryogen flow-through. Results from pressure decay tests show that liquid nitrogen stimulation clearly increases permeability, and repeated stimulations further increase the permeability. Acoustic velocities and amplitudes decreased significantly following cryo-stimulation indicating fracture creation. In the gas fracturing without the stimulation, breakdown (complete fracturing) occurs suddenly without any initial leaking, and major fracture planes form along the plane containing principal stress and intermediate stress directions as expected theoretically. However, in the gas fracturing after cryogenic stimulations, breakdown occurred gradually and with massive leaking due to thermal fractures created during stimulation. In addition, the major fracture direction does not necessarily follow the plane containing principal stress direction, especially at low confining stress levels. In tests, we observed that cryogenic stimulation seems to disrupt the internal stress field. The increase in borehole temperature after stimulation affects the permeability of the specimen. When a stimulated specimen is still cold, it maintains high permeability because fractures remain open and local thermal tension is maintained near the borehole. When the rock warms back, fractures close and permeability decreases. In these tests, we have not used proppants. Overall, fractures are clearly generated by low and high-pressure thermal shocks. The added pressure of the high-pressure thermal shocks helps to further propagate cryogenic fractures 1 2 3 4 5 6 7 8 9 2 generated by thermal shock. Breakdown pressure ...

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Compression Wave Velocity of Cylindrical Rock Specimens: Engineering Modulus Interpretation

Cited by 15 publications

References 3 publications

Effect of Partial Water Saturation on Attenuation Characteristics of Low Porosity Rocks

Effect of Partial Water Saturation on Attenuation Characteristics of Low Porosity Rocks

Evaluating the Dynamic Elastic Modulus of Concrete Using Shear-Wave Velocity Measurements

Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation

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