scholarly journals The investigation of the scale effect on porosity in Bashkirian limestones

2021 ◽  
Vol 21 (2) ◽  
pp. 137-147
Author(s):  
Damir I. Khassanov ◽  
◽  
Marat A. Lonshakov ◽  
Keyword(s):  
Physical Parameter ◽  
Scale Effect ◽  
Representative Elementary Volume ◽  
Core Size ◽  
Elementary Volume ◽  
Core Samples ◽  
Core Fragment ◽  
Volume Calculations ◽  
Diameter Core ◽  
Porosity Changes

The article presents the methodology of the representative elementary volume definition for two 1 m long whole core segments. Scientific articles focused on practical methods of representative volume calculations using various physical parameter fluctuations have been studied. Porosity values of every whole core fragment evaluated in two ways using the 7.3 cm diameter core samples in the first approach and the 3 cm diameter core samples in the second one have been compared. Particularities of the scale effect occurring in core samples and depending on core size and porosity type have been analyzed. The cause of porosity increase in big core samples has been determined. The reason due to which porosity changes are explained by fracture porosity occurring in core samples having big volumes has been found. The comparison between neutron log porosity and core porosity has been made. Reasons of similarities or differences of core and log data have been established.

scholarly journals The investigation of the porosity scale effect and elastic anisotropy in Bashkirian limestones

2021 ◽  
Vol 21 (3) ◽  
pp. 209-217
Author(s):  
Damir I. Khassanov ◽  
◽  
Oleg Yu. Andrushkevich ◽  
Marat A. Lonshakov ◽  
◽  
...  
Keyword(s):  
Physical Properties ◽  
Elastic Properties ◽  
Scale Effect ◽  
Elastic Anisotropy ◽  
Representative Elementary Volume ◽  
Elementary Volume ◽  
Core Samples ◽  
Core Fragment ◽  
Core Sampling

The article presents the methodology of the representative elementary volume definition for 1 m long whole core segments. Scientific articles focused on factors controlling elastic properties are analysed. Terms of additivity and nonadditivity for physical properties of rocks are discussed. The algorithm of core sampling including drilling out of three perpendicular core samples for estimation of elastic anisotropy was used. Porosity values of 1 m long whole core fragment evaluated in two ways using original core samples in the first approach and core samples having volume 133 cm3 in the second way have been compared. Peculiarities of scale effect of porosity in core samples of limestones are analysed.

scholarly journals New insights on homogenization for hexagonal-shaped composites as Cosserat continua

Meccanica ◽  
2021 ◽  
Author(s):  
Marco Colatosti ◽  
Nicholas Fantuzzi ◽  
Patrizia Trovalusci ◽  
Renato Masiani
Keyword(s):  
Continuum Theory ◽  
Representative Elementary Volume ◽  
Elementary Volume ◽  
Displacement Fields ◽  
Micropolar Continuum ◽  
Rigid Particles ◽  
Hexagonal Shape ◽  
Classical Models ◽  
Elastic Interfaces ◽  
Cosserat Continua

AbstractIn this work, particle composite materials with different kind of microstructures are analyzed. Such materials are described as made of rigid particles and elastic interfaces. Rigid particles of arbitrary hexagonal shape are considered and their geometry is described by a limited set of parameters. Three different textures are analyzed and static analyses are performed for a comparison among the solutions of discrete, micropolar (Cosserat) and classical models. In particular, the displacements of the discrete model are compared to the displacement fields of equivalent micropolar and classical continua realized through a homogenization technique, starting from the representative elementary volume detected with a numeric approach. The performed analyses show the effectiveness of adopting the micropolar continuum theory for describing such materials.

scholarly journals Estimating the Effect of Fractal Dimension on Representative Elementary Volume of Randomly Distributed Rock Fracture Networks

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Jing Zhang ◽  
Liyuan Yu ◽  
Hongwen Jing ◽  
Richeng Liu
Keyword(s):  
Fractal Dimension ◽  
Functional Relationship ◽  
Rock Fracture ◽  
Representative Elementary Volume ◽  
Width Ratio ◽  
Elementary Volume ◽  
Equivalent Permeability ◽  
Length Width ◽  
Rock Fracture Networks

The effect of fractal dimension (Df) on the determination of representative elementary volume (REV) was investigated through numerical experimentations, in which a new method was adopted to extract submodels that have different length-width ratios from original discrete facture networks (DFNs). Fluid flow in 1610 DFNs with different geometric characteristics of fractures and length-width ratios was simulated, and the equivalent permeability was calculated. The results show that the average equivalent permeability (KREV) at the REV size for DFNs increases with the increase in Df. The KREV shows a downward trend with increasing length-width ratio of the submodel. A strong exponent functional relationship is found between the REV size and Df. The REV size decreases with increasing Df. With the increment of the length-width ratio of submodels, the REV size shows a decreasing trend. The effects of length-width ratio and Df on the REV size can be negligible when Df≥1.5, but are significant when Df<1.5.

scholarly journals Determination of representative elementary volume (REV) for jointed rock masses exhibiting scale-dependent behavior: A numerical investigation

2021 ◽  
Author(s):  
Mehmet Sari
Keyword(s):  
Jointed Rock ◽  
Representative Elementary Volume ◽  
Elementary Volume ◽  
Rock Masses ◽  
Continuum Approach ◽  
Joint Spacing ◽  
Jointed Rock Masses ◽  
Equivalent Continuum ◽  
Equivalent Continuum Approach

Abstract Representative elementary volume (REV) is defined as the usual size of a rock mass structure beyond which its mechanical properties are homogenous and isotropic, and its behavior can be modeled using the equivalent continuum approach. Determination of REV is a complex problem in rock engineering due to its definition ambiguity and application area. This study is one of the first attempts to define a REV for jointed rock masses using the equivalent continuum approach. It is aimed to numerically search a ratio between the characteristic size of an engineering structure and pre-existing joint spacing, which are the two most important contributing elements in assessing REV. For this purpose, four hypothetical engineering cases were investigated using the RS2 (Phase2 v. 9.0) finite element (FE) analysis program. An underground circular opening with a constant diameter, an open-pit mine with varying bench heights, a single bench with a constant height, and an underground powerhouse cavern with a known dimension were executed for possible changes in the safety factor and total displacement measurements under several joint spacing values. Different cut-off REVs were calculated for FE models depending on the type of excavation and measurement method. An average REV size of 19.0, ranging between a minimum of 2 for tunnels and a maximum of 48 for slopes, was found in numerical analysis. The calculated sizes of REV were significantly larger than the range of values (5 to 10) commonly reported in the relevant geotechnical literature.

scholarly journals Upscaling of elastic properties in carbonates: A modeling approach based on a multiscale geophysical data set

2020 ◽  
Author(s):  
Jerome Fortin ◽  
Cedric Bailly ◽  
Mathilde Adelinet ◽  
Youri Hamon
Keyword(s):  
Elastic Properties ◽  
Wave Velocity ◽  
Representative Elementary Volume ◽  
P Wave ◽  
Elementary Volume ◽  
Data Set ◽  
Wave Velocities ◽  
P Wave Velocity ◽  
Ultrasonic Measurements ◽  
Seismic Scale

&lt;p&gt;Linking ultrasonic measurements made on samples, with sonic logs and seismic subsurface data, is a key challenge for the understanding of carbonate reservoirs. To deal with this problem, we investigate the elastic properties of dry lacustrine carbonates. At one study site, we perform a seismic refraction survey (100 Hz), as well as sonic (54 kHz) and ultrasonic (250 kHz) measurements directly on outcrop and ultrasonic measurements on samples (500 kHz). By comparing the median of each data set, we show that the P wave velocity decreases from laboratory to seismic scale. Nevertheless, the median of the sonic measurements acquired on outcrop surfaces seems to fit with the seismic data, meaning that sonic acquisition may be representative of seismic scale. To explain the variations due to upscaling, we relate the concept of representative elementary volume with the wavelength of each scale of study. Indeed, with upscaling, the wavelength varies from millimetric to pluri-metric. This change of scale allows us to conclude that the behavior of P wave velocity is due to different geological features (matrix porosity, cracks, and fractures) related to the different wavelengths used. Based on effective medium theory, we quantify the pore aspect ratio at sample scale and the crack/fracture density at outcrop and seismic scales using a multiscale representative elementary volume concept. Results show that the matrix porosity that controls the ultrasonic P wave velocities is progressively lost with upscaling, implying that crack and fracture porosity impacts sonic and seismic P wave velocities, a result of paramount importance for seismic interpretation based on deterministic approaches.&lt;/p&gt;&lt;p&gt;Bailly, C., Fortin, J., Adelinet, M., &amp; Hamon, Y. (2019). Upscaling of elastic properties in carbonates: A modeling approach based on a multiscale geophysical data set. Journal of Geophysical Research: Solid Earth, 124. https://doi.org/10.1029/2019JB018391&lt;/p&gt;

Accuracy and Upgrade Rates of Percutaneous Breast Biopsy: The Surgeon's Role

2010 ◽  
Vol 76 (10) ◽  
pp. 1084-1087 ◽  
Author(s):  
Windy Olaya ◽  
Won Bae ◽  
Jan Wong ◽  
Jasmine Wong ◽  
Sharmila Roy-Chowdhury ◽  
...  
Keyword(s):  
Needle Biopsy ◽  
Breast Imaging ◽  
Breast Biopsy ◽  
Imaging Study ◽  
Surgical Excision ◽  
Core Size ◽  
Image Guided ◽  
Core Samples ◽  
Limited Sampling ◽  
The Impact

We sought to evaluate the impact of needle core size and number of core samples on diagnostic accuracy and upgrade rates for image-guided core needle biopsies of the breast. A total of 234 patients underwent image-guided percutaneous needle biopsies and subsequent surgical excision. Large-core needles (9 gauge or less) were used in 14.5 per cent of cases and the remainder were performed with smaller core needles. More than four core samples were taken in 78.9 per cent of patients. In 71.8 per cent of cases, needle biopsy pathology matched surgical excision pathology. After surgical excision, upgraded pathology was revealed in 10.7 per cent of cases. Of 11 patients (52.4%) with benign needle core pathology who had upgraded final pathology on surgical excision, 10 had a Breast Imaging Recording and Data System score 4 or 5 imaging study. Lesions smaller than 10 mm were more likely to be misdiagnosed ( P = 0.01) or have upgraded pathology ( P = 0.009). Other predictors of upgraded pathology were patient age 50 years or older ( P = 0.03) and taking four or fewer core samples ( P = 0.003). Needle core size did not impact accuracy or upgrade rates. Surgeons should exercise caution when interpreting needle biopsy results with older patients, smaller lesions, and limited sampling. Discordant pathology and imaging still mandate surgical confirmation.

Sign in / Sign up

Export Citation Format

Share Document