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Acta Geotechnica - This article presents a new test prototype that leverages the 3D printing technique to create artificial particle assembles to provide auxiliary evidences that supports the... 相似文献
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Kido Ryunosuke Higo Yosuke Takamura Fukushi Morishita Ryoichi Khaddour Ghonwa Salager Simon 《Acta Geotechnica》2020,15(7):1745-1761
Acta Geotechnica - Water retention characteristics are important for modeling the mechanical and hydraulic behavior of partially saturated sand. It is well known that the soil water characteristic... 相似文献
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A tomographic imagery segmentation methodology for three-phase geomaterials based on simultaneous region growing 总被引：2，自引：2，他引：0
Mir Amid Hashemi Ghonwa Khaddour Bertrand François Thierry J. Massart Simon Salager 《Acta Geotechnica》2014,9(5):831-846
X-ray computed tomography is a powerful non-destructive technique used in many domains to obtain the three-dimensional representation of objects, starting from the reconstitution of two-dimensional images of radiographic scanning. This technique is now able to analyze objects within a few micron resolutions. Consequently, X-ray microcomputed tomography opens perspectives for the analysis of the fabric of multiphase geomaterials such as soils, concretes, rocks and ceramics. To be able to characterize the spatial distribution of the different phases in such complex and disordered materials, automated phase recognition has to be implemented through image segmentation. A crucial difficulty in segmenting images lies in the presence of noise in the obtained tomographic representation, making it difficult to assign a specific phase to each voxel of the image. In the present study, simultaneous region growing is used to reconstitute the three-dimensional segmented image of granular materials. First, based on a set of expected phases in the image, regions where specific phases are sure to be present are identified, leaving uncertain regions of the image unidentified. Subsequently, the identified regions are grown until growing phases meet each other with vanishing unidentified regions. The method requires a limited number of manual parameters that are easily determined. The developed method is illustrated based on three applications on granular materials, comparing the phase volume fractions obtained by segmentation with macroscopic data. It is demonstrated that the algorithm rapidly converges and fills the image after a few iterations. 相似文献
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An innovative device for determining the soil water retention curve under high suction at different temperatures 总被引：3，自引：3，他引：0
To characterise the water retention behaviour of fine soils, high suction values are applied. In this range of values, the
vapour equilibrium technique is usually used. This paper presents an innovative device, a sorption bench that permits the
determination of the water retention curve of soil. With this new testing method, the time required for testing is significantly
reduced. In addition, this apparatus enables the thermal conditions of a test to be controlled; thus, the applied suction
can be better controlled, and the water retention curve for different temperatures can be determined. Another valuable aspect
of the device is the adopted technical solution that permits weighing of the samples inside the desiccators at any time. Consequently,
the water content kinetics can be defined without disturbing the drying or wetting processes. 相似文献
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The reduction in volume for unsaturated soils wetted at constant total stress is indicated as capillary collapse. Several studies conducted on standard laboratory specimens (macro-scale) outlined the role of initial void ratio, confining pressure and matric suction on collapse onset. Conversely, few observations were made at grain scale, although an important influence of soil structure has been supposed since years. This paper investigated the collapse of coarse and fine sands derived from a pyroclastic soil of Southern Italy. The X-ray computed tomography was used to identify the mechanisms acting at grain scale and to measure the local variations of soil structure. The experimental procedure consisted in preparing remoulded unsaturated specimens and reducing the matric suction until the collapse occurred under self-weight. At different stages of the process, the sample was imaged by X-ray tomography. The experimental results provided original insight into: (1) transformation of soil structure during the wetting tests; (2) variation of porosity, water content and degree of saturation for the whole specimen; and (3) local variations of those variables in several representative sub-volumes. It is worth noting that collapse of coarse sand specimen occurred before saturation. This was also emphasized by the presence of macro-voids at collapse. 相似文献
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This paper aims to analyse the anisotropic features of behaviour of Opalinus Clay using the theory of plastic multi-mechanisms. The results of triaxial tests conducted with different load levels and directions showed that the mechanical behaviour of this shale is cross-anisotropic. The stiffer samples are those in which the loading direction is parallel to the bedding plane. This indicates that the preconsolidation stress depends on the orientation of the load with respect to the fabric of Opalinus Clay. It is proposed to interpret the observed cross-anisotropy with an elastoplastic model based on four plastic strain mechanisms that may be successively mobilised depending on the loading direction. The predicted stress–strain responses vary according to the directions of the space as a result of the hardening process, depending on the number of plastic strain mechanisms that have been mobilised. The numerical predictions show overall good agreement with the experimental data in terms of deviatoric stress versus axial strain, demonstrating that multi-mechanism plasticity is a suitable constitutive tool for the interpretation of the mechanical anisotropy of this shale. 相似文献
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The water retention capacity of geomaterials, and especially clayey soils, is sensitive to temperature changes as the physical mechanisms of retention, such as capillarity or adsorption, are affected by it. It is therefore a major issue to be able to define temperature-dependent behaviour of materials, especially for geo-energy and geo-environmental applications involving non-isothermal conditions. This paper presents results of experiments conducted on two representative materials: a hard clay (Opalinus clay) and a plastic clay (Boom clay), both of which have been considered as buffer materials for underground radioactive waste disposal, in Switzerland and Belgium, respectively. Two new devices were developed for this purpose to permit the analysis of water retention behaviour at different temperatures. The behaviour of these two materials at ambient (20 °C) and high temperature (80 °C) was observed and described through the evolution of the degree of saturation, the water content and the void ratio with respect to suction. It appears that the retention capability of the clays reduces significantly with an increase in temperature; on the other hand, the change in temperature had less of an effect on the total volume variation. 相似文献
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