Dilatational Wave Velocities and Dynamic Elastic Moduli of Ni‐Mn Alloys

Abstract. The accuracy of ground deformation modelling at active volcanoes is a principal requirement in volcanic hazard mitigation. However, the reliability of such models relies on the accuracy of the rock physical property (permeability and elastic moduli) input parameters. Unfortunately, laboratory-derived values on representative rocks are usually rare. To this end we have performed a systematic laboratory study on the influence of pressure and temperature on the permeability and elastic moduli of samples from the two most widespread lithified pyroclastic deposits at the Campi Flegrei volcanic district, Italy. Our data show that the water permeability of Neapolitan Yellow Tuff and a tuff from the Campanian Ignimbrite differ by about 1.5 orders of magnitude. As pressure (depth) increases beyond the critical point for inelastic pore collapse (at an effective pressure of 10–15 MPa, or a depth of about 750 m), permeability and porosity decrease significantly, and ultrasonic wave velocities and dynamic elastic moduli increase significantly. Increasing the thermal stressing temperature increases the permeability and decreases the ultrasonic wave velocities and dynamic elastic moduli of the Neapolitan Yellow Tuff; whereas the tuff from the Campanian Ignimbrite remains unaffected. This difference is due to the presence of thermally unstable zeolites within the Neapolitan Yellow Tuff. For both rocks we also find, under the same pressure conditions, that the dynamic (calculated from ultrasonic wave velocities) and static (calculated from triaxial stress-strain data) elastic moduli differ significantly. The choice of elastic moduli in ground deformation modelling is therefore an important consideration. While we urge that these new laboratory data should be considered in routine ground deformation modelling, we highlight the challenges for ground deformation modelling based on the heterogeneous nature (vertically and laterally) of the rocks that comprise the caldera at Campi Flegrei.

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Relationships between Dynamic Elastic Moduli in Shale Reservoirs

Energies ◽

10.3390/en13226001 ◽

2020 ◽

Vol 13 (22) ◽

pp. 6001

Author(s):

Sheyore John Omovie ◽

John P. Castagna

Keyword(s):

Organic Carbon ◽

Shear Modulus ◽

Elastic Moduli ◽

Volume Fraction ◽

P Wave ◽

Wave Velocities ◽

Shear Wave Velocities ◽

Average Formation ◽

Dynamic Elastic Moduli ◽

Shale Reservoirs

Sonic log compressional and shear-wave velocities combined with logged bulk density can be used to calculate dynamic elastic moduli in organic shale reservoirs. We use linear multivariate regression to investigate modulus prediction when shear-wave velocities are not available in seven unconventional shale reservoirs. Using only P-wave modulus derived from logged compressional-wave velocity and density as a predictor of dynamic shear modulus in a single bivariate regression equation for all seven shale reservoirs results in prediction standard error of less than 1 GPa. By incorporating compositional variables in addition to P-wave modulus in the regression, the prediction standard error is reduced to less than 0.8 GPa with a single equation for all formations. Relationships between formation bulk and shear moduli are less well defined. Regressing against formation composition only, we find the two most important variables in predicting average formation moduli to be fractional volume of organic matter and volume of clay in that order. While average formation bulk modulus is found to be linearly related to volume fraction of total organic carbon, shear modulus is better predicted using the square of the volume fraction of total organic carbon. Both Young’s modulus and Poisson’s ratio decrease with increasing TOC while increasing clay volume decreases Young’s modulus and increases Poisson’s ratio.

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Dynamic elastic moduli of a suspension of imperfectly bonded spheres

Mathematical Proceedings of the Cambridge Philosophical Society ◽

10.1017/s0305004100049318 ◽

1974 ◽

Vol 76 (3) ◽

pp. 587-600 ◽

Cited By ~ 63

Author(s):

A. K. Mal ◽

S. K. Bose

Keyword(s):

Elastic Material ◽

Elastic Waves ◽

Elastic Moduli ◽

Random Distribution ◽

Spherical Particles ◽

Shear Stresses ◽

Wave Velocities ◽

The Matrix ◽

Dynamic Elastic Moduli ◽

Earthquake Faults

AbstractAn isotropic elastic material containing a random distribution of identical spherical particles of another elastic material is considered. The bonding between the spheres and the matrix is imperfect, so that slip may occur at interfaces when stress is applied to the medium. The shear stresses at the interface is assumed to be proportional to the amount of slip. The velocity and attenuation of the average harmonic elastic waves propagating through such a medium are calculated. The results are valid to the lowest order in frequency for wave lengths long compared with the radius of the sphere. The dynamic elastic moduli are obtained from these results and are compared with available results for welded contact. The variations in the P and S wave velocities for propagation across earthquake faults is discussed.

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The permeability and elastic moduli of tuff from Campi Flegrei, Italy: implications for ground deformation modelling

Solid Earth Discussions ◽

10.5194/sed-5-1081-2013 ◽

2013 ◽

Vol 5 (2) ◽

pp. 1081-1123 ◽

Cited By ~ 1

Author(s):

M. J. Heap ◽

P. Baud ◽

P. G. Meredith ◽

S. Vinciguerra ◽

T. Reuschlé

Keyword(s):

Ultrasonic Wave ◽

Elastic Moduli ◽

Ground Deformation ◽

Laboratory Data ◽

Campi Flegrei ◽

Campanian Ignimbrite ◽

Wave Velocities ◽

Neapolitan Yellow Tuff ◽

Heterogeneous Nature ◽

Dynamic Elastic Moduli

Abstract. The accuracy of ground deformation modelling at active volcanoes is a principal requirement in volcanic hazard mitigation. However, the reliability of such models relies on the accuracy of the rock physical property (permeability and elastic moduli) input parameters. Unfortunately, laboratory-derived values on representative rocks are usually rare. To this end we have performed a systematic laboratory study of the influence of pressure and temperature on the permeability and elastic moduli of the two most widespread tuffs from the Campi Flegrei volcanic district, Italy. Our data show that the water permeability of Neapolitan Yellow Tuff and a tuff from the Campanian Ignimbrite differ by about two orders of magnitude, highlighting the heterogeneous nature of the tuffs at Campi Flegrei. As pressure (depth) increases beyond the critical point for inelastic pore collapse (at an effective pressure of 10–15 MPa, or a depth of about 750 m), permeability and porosity decrease significantly, and ultrasonic wave velocities and dynamic elastic moduli increase significantly. Increasing the thermal stressing temperature increases the permeability and decreases the ultrasonic wave velocities and dynamic elastic moduli of the Neapolitan Yellow Tuff; whereas the tuff from the Campanian Ignimbrite remains unaffected. This difference is due the presence of thermally unstable zeolites within the Neapolitan Yellow Tuff. For both rocks we also find, under the same pressure conditions, that the dynamic (calculated from ultrasonic wave velocities) and static (calculated from triaxial stress-strain data) elastic moduli differ significantly. The choice of elastic moduli in ground deformation modelling is therefore an important consideration. While we urge that these new laboratory data should be considered in routine ground deformation modelling, we highlight the heterogeneous nature of the rocks that comprise the caldera at Campi Flegrei.

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