Shear weakening for different lithologies observed at different saturation stages

Diethart-Jauk, Elisabeth; Gegenhuber, Nina

doi:10.1016/j.jappgeo.2017.11.011

Cited by 17 publications

(8 citation statements)

References 11 publications

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“…Furthermore, various ultrasonic results have shown that shear modulus does not always remain constant after fluid saturation as predicted by Gassmann's theory (Baechle et al, ; Green & Wang, ; Vialle & Vanorio, ). The variation of shear modulus for a fluid‐saturated rock, either a net increase (strengthening) or a net decrease (weakening), has been attributed to the combined effect of several factors, such as fluid‐solid interaction, clay degradation or expansion, and viscous coupling (Cadoret, ; Diethart‐Jauk & Gegenhuber, ; Khazanehdari & Sothcott, ; Tutuncu & Sharma, ). Data about the fluid saturation effect on shear modulus are comparatively rare at seismic frequencies.…”

Section: Introductionmentioning

confidence: 99%

Fluid Substitution and Shear Weakening in Clay‐Bearing Sandstone at Seismic Frequencies

et al. 2019

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Using the forced oscillation method and the ultrasonic transmission method, we measure the elastic moduli of a clay‐bearing Thüringen sandstone under dry and water‐saturated conditions in a broad frequency band at [0.004–10, 106] Hz for different differential pressures up to 30 MPa. Under water‐saturated condition, clear dispersion and attenuation for Young's modulus, Poisson's ratio, and Bulk modulus are observed at seismic frequencies, except for shear modulus. The measured dispersion and attenuation are mainly attributed to the drained/undrained transition, which considers the experimentally undrained boundary condition. Gassmann's predictions are consistent with the measured undrained bulk moduli but not with the shear moduli. Clear shear weakening is observed, and this water‐softening effect is stronger at seismic frequencies than at ultrasonic frequencies where stiffening effect related to squirt flow may mask real shear weakening. The reduction in surface free energy due to chemical interaction between pore fluid and rock frame, which is not taken into account by Gassmann's theory, is the main reason for the departure from Gassmann's predictions, especially for this rock containing a large number of clay minerals.

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Section: Introductionmentioning

confidence: 99%

Fluid Substitution and Shear Weakening in Clay‐Bearing Sandstone at Seismic Frequencies

et al. 2019

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“…The relation between calculating the magnetic eld due to a rectangular prism is (presented by Bhattacharya (Bhattacharyya & Chan, 1977;Bhattacharyya, 1980 F̂ is the earth's magnetic eld, and each prism has magnetization of M, and the dimensions x 1 ≤ x ≤ x 2 , y 1 ≤ y ≤ y 2 , and z 1 ≤ z ≤ ∞. To calculate the total anomaly observed at the origin of the coordinates resulting from a rectangular prism extending from the depths z a to z b , rst should calculated Equation 3for a prism with a depth of z a and magnetization M, then for a prism with a depth of z b and magnetization -M. By coding in MATLAB using equation 3, the anomaly of the total magnetic eld caused by a prism can be calculated at a viewpoint (Diethart-Jauk & Gegenhuber, 2018;Hubbert, 1948;Lelièvre & Oldenburg, 2006;Stocco et al, 2009).…”

Section: Methodsmentioning

confidence: 99%

Estimation of Depth, Physical Parameters, and Location using Nonlinear Inverse Modeling of Magnetic Data by Bhattacharya Method in a field of NW Iran

Hosseini

Khah²,

Kianoush

et al. 2023

Preprint

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Geophysical studies are utilized as one of the main steps in exploration that must be performed before exploratory drilling due to the high cost of excavation and its related heavy machinery and reduction of the exploration cost. One of the most critical geophysical issues in estimating the physical and geometric parameters is the store carrying out using the residual magnetic anomaly reduction. These parameters include depth, volume, shape factor, and type of storage. The present geophysical study aims to prepare and model magnetic data for proposed drilling sites in the Baba Ali Iron ore deposit in the Hamedan province of Iran. Inverse modeling is one of the most efficient interpretive methods of potential field data. In this study, the Bhattacharya method in MATLAB software is used to minimize the target function and potential field data to create the best fit for magnetic data. In this modeling, the graphs of the residual anomaly and model showed an excellent conformation two-dimensionally. Also, 3D modeling reconstructs the properties of the productive resources of anomalies correctly. After preparation of total magnetic maps, it was found out that the magnetic lens in four anomalies with surface depths of 20, 50, and 50 meters is estimated for this zone. Their specific gravity was 4.77 t / m3, and their initial storage capacity was 95,400 tones at most. Also, exploratory excavation is proposed to complete the preliminary explorations of the specified region by inverse modeling for the three points.

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“…( 3) for a prism with a depth of z a and magnetization M, then for a prism with a depth of z b and magnetization -M. Using MATLAB coding and Eq. ( 3), the anomaly of the total magnetic field caused by a prism can be calculated (Diethart-Jauk & Gegenhuber, 2018;Hubbert, 1948;Lelièvre & Oldenburg, 2006;Stocco et al, 2009). MATLAB coding developed the total magnetic field anomaly; however, the results were depicted in Geosoft and Model Vision commercial softwares to have more precise and clear figures.…”

Section: Magnetic Effect Of a 3d Mass In A Forward Methodsmentioning

confidence: 99%

Geobody Estimation by Bhattacharyya Method Utilizing Nonlinear Inverse Modeling of Magnetic Data in Baba-Ali Iron Deposit, NW Iran

Kianoush

Khah²,

Hosseini

et al. 2023

Preprint

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Geophysical investigations are one of the leading efforts in any exploration project that must be performed ahead of time due to the high excavation expenditures, heavy machinery, and cost reduction. One of the essential geophysical concerns is the estimation of the physical and geometrical parameters of the reserve (geobody), which is done by exploiting the nonlinear inverse modeling of magnetic data. These parameters include depth, volume, shape factor, and type of storage. The present investigation aims to prepare and model magnetic data for proposed drilling sites in the Baba Ali Iron ore deposit in the Hamedan province of Iran. The areal and depth extent of the iron ore geobody was unknown. The Bhattacharyya method by MATLAB software coding was used to minimize the target function and potential field data and create the best fit for the magnetic data. The residual anomaly and model graphs exhibited an excellent two-dimensional conformation in this modeling. Also, 3D modeling correctly reconstructs the properties of the productive resources of anomalies. After preparing full magnetic maps, the magnetic lenses distinguished in four anomalies of surface depths, 20, 50, and deeper than 50 meters for this zone. This magnetite lens for the first zone was estimated based on filters applied on the entire magnetic map so that the lens's depth is trivial and almost zero. Their specific gravity is calculated as 4.77 t/m3, and their initial storage capacity is suggested to be about 95,400 tones at most. Finally, to complete the preliminary explorations of the specified area, exploratory drilling is suggested for three points by inverse modeling.

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Shear weakening for different lithologies observed at different saturation stages

Cited by 17 publications

References 11 publications

Fluid Substitution and Shear Weakening in Clay‐Bearing Sandstone at Seismic Frequencies

Fluid Substitution and Shear Weakening in Clay‐Bearing Sandstone at Seismic Frequencies

Estimation of Depth, Physical Parameters, and Location using Nonlinear Inverse Modeling of Magnetic Data by Bhattacharya Method in a field of NW Iran

Geobody Estimation by Bhattacharyya Method Utilizing Nonlinear Inverse Modeling of Magnetic Data in Baba-Ali Iron Deposit, NW Iran

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