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Journal ArticleDOI: 10.1080/1064119X.2019.1698680

X-ray analysis on the effect of sample preparation on the microstructure of calcareous sands

04 Mar 2021-Marine Georesources & Geotechnology (Taylor & Francis)-Vol. 39, Iss: 3, pp 302-311
Abstract: The behavior of a sandy soil in laboratory tests is highly influenced by the sedimentation technique. In this study, a calcareous sand from the reclamation site in Persian Gulf is used as the mater...

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Topics: Calcareous (52%)
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Journal ArticleDOI: 10.1080/1064119X.2020.1775327
Jinquan Shi1, Wim Haegeman1, Joren Andries2Institutions (2)
Abstract: This study examines the effect of the initial fabric on the coefficient of the lateral earth pressure at rest K-0, the undrained monotonic loading strength and the liquefaction resistance of a calcareous sand from a reclamation land in Persian Gulf. K(0)consolidation, undrained compression and extension and cyclic undrained loading triaxial tests are performed on laboratory samples reconstituted by air and water pluviation, dry and moist tamping and dry funnel deposition methods. Test results show that the air pluviation and moist tamping samples own the highest and the lowest K(0)respectively. All the samples at medium loose and medium dense states show strain hardening when subjected to undrained monotonic loading. The air pluviation samples are more contractive than the other samples at the phase transformation points and the moist tamping samples exhibit an over-consolidated behavior. In the cyclic loading tests, the air pluviation and the moist tamping samples exhibit the lowest and the highest liquefaction resistance. It is shown that the evaluation and comparison of the cyclic undrained strength of various sands should take the sample preparation method into consideration scrupulously. The test results also indicate that although the mechanical property of soil sample is influenced by the fabric differences induced by sample preparation method, other factors such as homogeneity and stress history should not be neglected.

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8 Citations


Journal ArticleDOI: 10.1016/J.SOILDYN.2020.106381
Jinquan Shi1, Wim Haegeman1, Tao XuInstitutions (1)
Abstract: This study investigates the effect of non-plastic fines on the anisotropic smalls strain stiffness of a calcareous sand by conducting multidirectional bender element tests. G H H , G H V and G V H are evaluated on both horizontal and vertical planes and the stiffness anisotropy, considering the effect of fine content, is studied. The models for predicting small strain shear modulus G 0 of the calcareous sands are modified. Test results show that G 0 decreases with the increase of the fine content until a threshold fine content is reached. The stiffness anisotropy drops with the increases of the fine content. The modified Hardin equation provides a better prediction than the modified Wichtmann equation and the Payan equation.

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Topics: Shear modulus (52%)

1 Citations


Journal ArticleDOI: 10.1680/JGEOT.20.P.121
03 Nov 2021-Geotechnique
Abstract: High-quality undisturbed samples of fluvial sand were obtained from the field using the ground freezing technique. In the laboratory, the in situ void ratio of these high-quality undisturbed frozen...

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Topics: Void ratio (54%), Ground freezing (53%), Sampling (statistics) (50%)

Open accessJournal ArticleDOI: 10.1007/S10035-021-01169-4
Amy Ferrick1, Vanshan Wright2, Vanshan Wright3, Michael Manga1  +1 moreInstitutions (3)
01 Jan 2022-Granular Matter
Abstract: The orientation of, and contacts between, grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. Using x-ray computed microtomography, we compare the microstructure of naturally-deposited beach sands and laboratory sands created by air pluviation in which samples are formed by raining sand grains into a container. We find that naturally-deposited sands have a narrower distribution of coordination number (i.e., the number of grains in contact) and a broader distribution of grain orientations than pluviated sands. The naturally-deposited sand grains orient inclined to the horizontal, and the pluviated sand grains orient horizontally. We explain the microstructural differences between the two different depositional methods by flowing water at beaches that re-positions and reorients grains initially deposited in unstable grain configurations.

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Book ChapterDOI: 10.1007/978-3-030-79650-1_6
Jinquan Shi1, Wim Haegeman2Institutions (2)
19 Jul 2021-
Abstract: This study examines the effect of the sample preparation method on the empirical-determined constants in the Hardin equation for predicting the small strain stiffness of a calcareous sand. Multi-directional bender element tests are performed in a triaxial cell under isotropic and anisotropic consolidation stress paths. Five sample preparation methods as air and water pluviation, dry and moist tamping and dry funnel deposition are used as the sample reconstitution techniques. Test results show that the sample preparation method has a considerable impact on the constants in the Hardin equation. Moist tamping samples show the highest A and the lowest n compared with the samples made by the other preparation methods. The lowest A and the highest n are found in the dry funnel deposition method. It is concluded that a higher A always corresponds with a lower n and the magnitude of the constants are related to the stability of the sample fabric. It is also shown that the constants determined in the anisotropic consolidation tests correspond well with the constants in the isotropic consolidation.

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References
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34 results found


Open accessJournal ArticleDOI: 10.1016/J.EARSCIREV.2013.04.003
Veerle Cnudde1, Matthieu Boone1Institutions (1)
Abstract: High-resolution X-ray Computed Tomography (HRXCT) or micro-CT (μCT) is a frequently used non-destructive 3D imaging and analysis technique for the investigation of internal structures of a large variety of objects, including geomaterials. Although the possibilities of X-ray micro-CT are becoming better appreciated in earth science research, the demands on this technique are also approaching certain physical limitations. As such, there remains a lot of research to be done in order to solve all the technical problems that occur when higher demands are put on the technique. In this paper, a review of the principle, the advantages and limitations of X-ray CT itself are presented, together with an overview of some current applications of micro-CT in geosciences. One of the main advantages of this technique is the fact that it is a non-destructive characterization technique which allows 4D monitoring of internal structural changes at resolutions down to a few hundred nanometres. Limitations of this technique are the operator dependency for the 3D image analysis from the reconstructed data, the discretization effects and possible imaging artefacts. Driven by the technological and computational progress, the technique is continuously growing as an analysis tool in geosciences and is becoming one of the standard techniques, as is shown by the large and still increasing number of publications in this research area. It is foreseen that this number will continue to rise, and micro-CT will become an indispensable technique in the field of geosciences.

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904 Citations


Journal ArticleDOI: 10.1520/GTJ10364J
Abstract: A specimen preparation procedure is presented that offers an improved method of preparing reconstituted sand specimens for cyclic triaxial testing. The method leads to more consistent and repeatable test results. This procedure (1) minimizes particle segregation, (2) can be used for compacting most types of sands having a wide range in relative densities, and (3) permits determination of the optimum cyclic strength of a given sand at a given dry unit weight.

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837 Citations


Journal ArticleDOI: 10.1680/GEOT.2010.60.5.315
01 May 2010-Geotechnique
Abstract: The objective of this work was to observe and quantify the onset and evolution of localised deformation processes in sand with grain-scale resolution. The key element of the proposed approach is combining state-of-the-art X-ray micro tomography imaging with three-dimensional volumetric digital image correlation techniques. This allows not only the grain-scale details of a deforming sand specimen to be viewed, but also, and more importantly, the evolving three-dimensional displacement and strain fields throughout loading to be assessed. X-ray imaging and digital image correlation have been in the past applied individually to study sand deformation, but the combination of these two methods to study the kinematics of shear band formation at the grain scale is the first novel aspect of this work. Moreover, the authors have developed a completely original grain-scale volumetric digital image correlation method that permits the characterisation of the full kinematics (i.e. three-dimensional displacements and rotations) of all the individual sand grains in a specimen. The results obtained using the discrete volumetric digital image correlation confirm the importance of grain rotations associated with strain localisation.

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Topics: Digital image correlation (63%), Shear band (50%), Displacement (vector) (50%) ... show more

437 Citations


Journal ArticleDOI: 10.1016/J.NIMA.2007.05.073
Abstract: The technique of X-ray microtomography using X-ray tube radiation offers an interesting tool for the non-destructive investigation of a wide range of materials. A major challenge lies in the analysis and quantification of the resulting data, allowing for a full characterization of the sample under investigation. In this paper, we discuss the software tools for reconstruction and analysis of tomographic data that are being developed at the UGCT. The tomographic reconstruction is performed using Octopus, a high-performance and user-friendly software package. The reconstruction process transforms the raw acquisition data into a stack of 2D cross-sections through the sample, resulting in a 3D data set. A number of artifact and noise reduction algorithms are integrated to reduce ring artifacts, beam hardening artifacts, COR misalignment, detector or stage tilt, pixel non-linearities, etc. These corrections are very important to facilitate the analysis of the 3D data. The analysis of the 3D data focuses primarily on the characterization of pore structures, but will be extended to other applications. A first package for the analysis of pore structures in three dimensions was developed under Matlab®. A new package, called Morpho+, is being developed in a C++ environment, with optimizations and extensions of the previously used algorithms. The current status of this project will be discussed. Examples of pore analysis can be found in pharmaceuticals, material science, geology and numerous other fields.

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Topics: Tomographic reconstruction (52%), Software (50%)

344 Citations


Journal ArticleDOI: 10.1061/AJGEB6.0000387
Abstract: The results of undrained stress controlled cyclic triaxial tests indicated that the dynamic strength of saturated sands, remolded to the same density by different compaction procedures, was significantly different. Variations in the dynamic strength of Monterey No.0 sand were found to be in the order of —100%; however, tests on other sands indicated that the magnitude of the effect of the method of preparation used may be a function of the type of sand. Fabric studies and electrical conductivity measurements indicated that the orientation and arrangement of the contacts between sand grains were probably the primary reasons for the observed differences in the dynamic strength of Monterey No.0 sand. Comparisons indicated that specimens prepared by moist tamping or moist vibratory compaction would exhibit dynamic strengths most similar to those of undisturbed samples; however, in most cases, the strength of undisturbed samples ranged from 0% to 45% higher than that of samples prepared by moist tamping.

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Topics: Soil liquefaction (52%)

320 Citations


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