Packing Density and Overconsolidation Ratio Effects on the Mechanical Response of Granular Soils

Many electrical and electromagnetic (EM) methods operate at MHz frequencies, at which the interfacial polarization occurring at the solid-liquid interface in geologic materials may dominate the electrical signals. To correctly interpret electrical/EM measurements, it is therefore critical to understand how the interfacial polarization influences the effective electrical conductivity and permittivity spectra of geologic materials. We have used pore-scale simulation to study the role of material texture and packing in interfacial polarization in water-saturated granular soils. Synthetic samples with varying material textures and packing densities are prepared with the discrete element method. The effective electrical conductivity and permittivity spectra of these samples are determined by numerically solving the Laplace equation in a representative elementary volume of the samples. The numerical results indicate that the effective permittivity of granular soils increases as the frequency decreases due to the polarizability enhancement from the interfacial polarization. The induced permittivity increment is mainly influenced by the packing state of the samples, increasing with the packing density. Material textures such as the grain shape and size distribution may also affect the permittivity increment, but their effects are less significant. The frequency characterizing the interfacial polarization (i.e., the characteristic frequency) is mainly related to the electrical contrast of the solid and water phases. The model based on the traditional differential effective medium (DEM) theory significantly underestimates the permittivity increment by a factor of more than two and overestimates the characteristic frequency by approximately 1 MHz. These inaccurate predictions are due to the fact that the electrical interactions between neighboring grains are not considered in the DEM theory. A simple empirical equation is suggested to scale up the theoretical depolarization factor of grains entering the DEM theory to account for the interaction of neighboring grains in granular soils.

Exploring the mechanical response of low-carbon soil improvement mixtures

Canadian Geotechnical Journal ◽

10.1139/cgj-2021-0087 ◽

2021 ◽

Author(s):

Alessandro Fraccica ◽

Giovanni Spagnoli ◽

Enrique E. Romero Morales ◽

Marcos Arroyo ◽

Rodrigo Gómez

Keyword(s):

Colloidal Silica ◽

Mechanical Response ◽

Ground Improvement ◽

Soil Improvement ◽

Silty Sand ◽

Triaxial Tests ◽

Granular Soils ◽

Low Carbon ◽

Cyclic Triaxial Tests ◽

Curing Conditions

As society moves towards decarbonisation it is important to assess the hydro-mechanical behaviour of binders that could offer a low-carbon alternative to Portland cement in ground improvement technologies. This work considers two such alterna-tives: one still largely unexplored (metakaolin-based geopolymers) and a better known one (colloidal silica). Results from unconfined compressive strength, permeability tests, undrained monotonic and cyclic triaxial tests on granular soils (sand and silty sand) treated with those two binders are presented and discussed, emphasizing simili-tudes and differences with the response of similar soils treated with other conventional and unconventional binders. Effects of silt content, curing conditions and soil/binder ratios are examined. Both colloidal silica and metakaolin-based geopolymer signifi-cantly improve the mechanical properties of the treated soils, although the geopolymer results in a stronger and stiffer material. Both treatments reduce much the permeabil-ity of the treated soil, but the reduction achieved with CS is larger.

Threshold silt content dependency on particle morphology (shape and size) of granular materials: review with new evidence

Acta geotechnica slovenica ◽

10.18690/actageotechslov.18.1.28-40.2021 ◽

2021 ◽

Vol 18 (1) ◽

pp. 28-40

Author(s):

Abdellah Cherif Taiba ◽

Youcef Mahmoudi ◽

Wiebke Baille ◽

Torsten Wichtmann ◽

Mostefa Belkhatir

Keyword(s):

Packing Density ◽

Mechanical Response ◽

Particle Morphology ◽

Silt Content ◽

Granular Assemblies ◽

Theoretical Approaches ◽

Particle Characteristics ◽

Recorded Data ◽

New Evidence ◽

Shape And Size

The threshold silt content is well known as a key parameter affecting the mechanical response of binary granular assemblies considering particle characteristics (size and shape). In this context, the threshold silt content (TSC) is determined from different laboratory tests based on packing density response (emax and emin versus silt content «Sc») and theoretical approaches proposed by several researchers in the specialized published literature using the characteristics of host sand and silt [emax(sand), emin(sand) , emax(silt) , emin(silt) , Gs , Gf and x]. The analysis of the recorded data indicates that the TSC derived from the (emax) curve appears more reliable than that obtained from the (emin) one. Moreover, it is found that the proposed analytical methods are suitable to quantify the threshold silt content (TSC) than that determined experimentally using the packing density (emax and emin). In addition, the test results show that the new introduced ratios [(D50s×As)/(D50f×Af)] and [(Cus×As)/(Cuf×Af)] determined based on particle characteristics (shape and size) appear as appropriate parameters for predicting the threshold silt content (TSC) of sand-silt mixture of the compiled data from the published literature as well as that of the present research related to Chlef sand, Fontainebleau sand and Hostun sand mixed with Chlef silt.

The nanogranular acoustic signature of shale

Geophysics ◽

10.1190/1.3097887 ◽

2009 ◽

Vol 74 (3) ◽

pp. D65-D84 ◽

Cited By ~ 41

Author(s):

J. Alberto Ortega ◽

Franz-Josef Ulm ◽

Younane Abousleiman

Keyword(s):

Packing Density ◽

Mechanical Response ◽

Volume Fraction ◽

Elastic Anisotropy ◽

Dominant Role ◽

Acoustic Properties ◽

Length Scales ◽

Micromechanics Model ◽

Stiffness Reduction ◽

Acoustic Signature

A multiscale, micromechanics model has been developed for the prediction of anisotropic acoustic properties of shale. The model is based on the recently identified nanogranular mechanical response of shale through indentation experiments. It recognizes the dominant role of the anisotropic elastic properties of compacted clay in the anisotropic elasticity of shale at different length scales compared to contributions of shape and orientation of particles. Following a thorough validation at multiple length scales using mineral elasticity data, nanoindentation experiment results, and ultrasonic pulse velocity tests, the model predictions compare adequately with measurements on kerogen-free and kerogen-rich shales and shaley sandstones. The acoustic signature of shale thus is found to be controlled by two volumetric parameters that synthesize the porosity and mineralogy information: the clay-packing density and the silt inclusion volume fraction. Through a series of dimensionless isoparametric plots, the micromechanics model predicts trends of increasing elastic anisotropy with increasing clay-packing density (or decreasing porosity), which correspond to the intrinsic mechanical response of unfractured shale, and quantifies the stiffness reduction induced by the presence of kerogen.

Comparison of Substructures Between Uniaxial and Biaxial Deformation in 1100-0 Aluminum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096989 ◽

1981 ◽

Vol 39 ◽

pp. 52-53

Author(s):

D. L. Rohr ◽

S. S. Hecker

Keyword(s):

Plastic Strain ◽

Cell Walls ◽

Room Temperature ◽

Mechanical Response ◽

Biaxial Tension ◽

Initial Deformation ◽

Uniaxial Deformation ◽

Biaxial Deformation ◽

Stress States ◽

Comprehensive Study

As part of a comprehensive study of microstructural and mechanical response of metals to uniaxial and biaxial deformations, the development of substructure in 1100 A1 has been studied over a range of plastic strain for two stress states.Specimens of 1100 aluminum annealed at 350 C were tested in uniaxial (UT) and balanced biaxial tension (BBT) at room temperature to different strain levels. The biaxial specimens were produced by the in-plane punch stretching technique. Areas of known strain levels were prepared for TEM by lapping followed by jet electropolishing. All specimens were examined in a JEOL 200B run at 150 and 200 kV within 24 to 36 hours after testing.The development of the substructure with deformation is shown in Fig. 1 for both stress states. Initial deformation produces dislocation tangles, which form cell walls by 10% uniaxial deformation, and start to recover to form subgrains by 25%. The results of several hundred measurements of cell/subgrain sizes by a linear intercept technique are presented in Table I.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165641 ◽

1996 ◽

Vol 54 ◽

pp. 636-637

Author(s):

D. L. Callahan

Keyword(s):

Plastic Deformation ◽

Aluminum Nitride ◽

Mechanical Response ◽

Three Dimensional ◽

Bright Field Image ◽

Perfectly Plastic ◽

Contrast Analysis ◽

Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

Effect of Fabric on Low-Strain Stiffness Properties of Granular Soils

Geo-Congress 2014 Technical Papers ◽

10.1061/9780784413272.065 ◽

2014 ◽

Author(s):

Chrysovalantis Tsigginos ◽

Mourad Zeghal

Keyword(s):

Granular Soils ◽

Stiffness Properties

Mechanical Response of Basalt Fiber Asphalt Pavement with Low Temperature-Load Coupling in Heavy Frozen Areas

CICTP 2020 ◽

10.1061/9780784483053.158 ◽

2020 ◽

Author(s):

Hua Wu ◽

Aiqin Shen ◽

Yinchuan Guo ◽

Zhenghua Lyu ◽

Li Fan

Keyword(s):

Low Temperature ◽

Mechanical Response ◽

Asphalt Pavement ◽

Basalt Fiber ◽

Temperature Load

The Mechanical Response of Aligned Carbon Nanotube Mats via Transmitted Laser Intensity Measurements

10.1557/proc-1142-jj16-04 ◽

2008 ◽

Author(s):

Christian Deck ◽

Chinung Ni ◽

Kenneth Vecchio ◽

Prabhakar Bandaru

Keyword(s):

Carbon Nanotube ◽

Mechanical Response ◽

Laser Intensity ◽

Intensity Measurements

Low-Dielectric-Constant Materials for ULSI Interlayer-Dielectric Applications

MRS Bulletin ◽

10.1557/s0883769400034151 ◽

1997 ◽

Vol 22 (10) ◽

pp. 19-27 ◽

Cited By ~ 86

Author(s):

Wei William Lee ◽

Paul S. Ho

Keyword(s):

Packing Density ◽

Propagation Delay ◽

Single Chip ◽

Crosstalk Noise ◽

Metal Line ◽

Total Delay ◽

Interlayer Dielectric ◽

Low Dielectric ◽

Interconnect Delay ◽

Interconnect Technology

Continuing improvement of microprocessor performance historically involves a decrease in the device size. This allows greater device speed, an increase in device packing density, and an increase in the number of functions that can reside on a single chip. However higher packing density requires a much larger increase in the number of interconnects. This has led to an increase in the number of wiring levels and a reduction in the wiring pitch (sum of the metal line width and the spacing between the metal lines) to increase the wiring density. The problem with this approach is that—as device dimensions shrink to less than 0.25 μm (transistor gate length)—propagation delay, crosstalk noise, and power dissipation due to resistance-capacitance (RC) coupling become significant due to increased wiring capacitance, especially interline capacitance between the metal lines on the same metal level. The smaller line dimensions increase the resistivity (R) of the metal lines, and the narrower interline spacing increases the capacitance (C) between the lines. Thus although the speed of the device will increase as the feature size decreases, the interconnect delay becomes the major fraction of the total delay and limits improvement in device performance.To address these problems, new materials for use as metal lines and interlayer dielectrics (ILD) as well as alternative architectures have been proposed to replace the current Al(Cu) and SiO2 interconnect technology.