Determining representative elementary volume size of in-situ expansive soils subjected to drying-wetting cycles through field test

The combination of pump-and-treat and in situ chemical oxidation processes can effectively accelerate the remediation of DNAPL pollutant in groundwater.

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

Meccanica ◽

10.1007/s11012-021-01355-x ◽

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.

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

Geofluids ◽

10.1155/2018/7206074 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 1

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.

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

10.21203/rs.3.rs-847473/v1 ◽

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.

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

10.5194/egusphere-egu2020-18106 ◽

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

<p>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.</p><p>Bailly, C., Fortin, J., Adelinet, M., & 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</p>

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The Use of Geogrids in Mitigating Pavement Defects on Roads Built over Expansive Soils

Rwanda Journal of Engineering Science Technology and Environment ◽

10.4314/rjeste.v4i1.4 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Richard Shumbusho ◽

Gurmel S. Ghataora ◽

Michael P.N. Burrow ◽

Digne R. Rwabuhungu

Keyword(s):

Seasonal Changes ◽

Expansive Soils ◽

Expansive Soil ◽

Real Field ◽

Experimental Program ◽

Swelling Potential ◽

Swelling Behaviour ◽

Wetting And Drying ◽

Potential Benefits

This study was conducted to investigate the potential benefits of using geogrids in mitigating pavement defects notably roughness and longitudinal cracking on pavements built over expansive soils. The seasonal changes of expansive soils (periodic wetting and drying) cause detrimental effects on the overlying road pavements. Such detrimental behavior of expansive soils was simulated in a controlled laboratory environment through allowing cyclic wetting and drying of an expansive soil underlying a pavement section. The shrink/swell effects of the expansive soil subgrade were examined through monitoring its change in moisture, and measuring deformation of overlying pavement section. The experimental study suggested that a geogrid layer in a reinforced pavement section can reduce surface differential shrinking and swelling deformation resulting from underlying expansive soils by a factor of 2 and 3 respectively in comparison to unreinforced section. Given that an oedometer test which is typically used to predict swelling potential of expansive soils is known to overpredict in-situ soil swell, experimental program also investigated quantitatively the extent to which the oedometer can overestimate swelling behaviour of the real-field scenarios. It was found that oedometer percent swell can overpredict in-situ swelling behaviour of the expansive soil by a factor ranging between 2 and 10 depending upon the period over which the in-situ expansive soil has been in contact with water.

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