1,720,986 research outputs found
Tomography data for interparticle contact detection analysis in spheroidal granular packings
No full textThis collection contains a series of synchrotron XCT scans on a hexagonal close-packed arrangement of soda-glass pellets. The field of view (FOV) diameter is 68.9 mm in diameter, approximately, and the nominal individual pellet diameter is 10 mm. The detector pixel size is 21 microns for all scans. The pellets were arranged in three horizontal lattices (layers). The middle and top lattices were separated by a layer of polyethylene film (cling film), while the bottom and middle layer were fully-contacting. Each file corresponds to a scan of either the bottom contacting or top non-contacting lattice pair. Thus, each filename includes a 'top' and 'bot' identifier. Acquisition parameters (number of projections, exposure time per projection, rotation range and sample position) were varied to achieve different image qualities and are included in 'README.txt'. All but scan A5 were local scans; scan A5 is a full-field scan acquired using the 'half-acquisition' method. Tomographic reconstruction was carried out using filtered back-projection in Savu. After reconstruction, a 3D median filter (kernel size = 2) and an anisotropic diffusion filter (diffusion threshold = 100; iterations = 2) were used to reduce noise. Data was acquired using Beamline I12-JEEP at Diamond Light Source (proposal NT26307-1). Please read README.txt Copyright 2021 Diamond Light Source Ltd. Licensed under the Apache License, Version 2.0.</span
Mechanical behaviour of low–medium density destructured White Chalk
No full textLow- and medium-density White Chalk often destructures during civil engineering works, forming a putty that exhibits problematic low strengths in the short term but may build-up strength with time. The underlying mechanisms that control the mechanical performance of the material are not well understood. This paper explores the prospect of developing a framework to characterise the behaviour of chalk putty. To this end, triaxial tests were carried out using low- and medium-density reconstituted chalks produced by different methods. Using void ratio against mean effective stress results, a unique critical state line (CSL) is proposed, regardless of parent rock origin or the crushing process used to generate the putty material. The CSL was also found to satisfactorily fit independent test data by various authors, even though each independent sample material may have had different ‘intrinsic’ CSLs. This was suggested to stem from the similar particle characteristics of the chalks used. An assessment of the ageing effect indicates increases in strength as a result of densification due to consolidation and secondary compression, however, the end-of-test state could still be described using the CSL
Laboratory Investigation of Shaft Friction in Displacement Piles Installed in Chalk
No full textThis dataset supports the thesis entitled 'The Shaft Capacity of Small Displacement Piles in Chalk' by Alvarez Borges and includes results from soil mechanics tests and computed tomography analysis.</span
The 1D normal compression line and structure permitted space of low-medium density chalk
No full textThe one-dimensional (1D) normal compression behaviour of low–medium density chalk is investigated by way of high-pressure oedometer tests on intact and reconstituted specimens. Test results reveal that a single 1D normal compression line (NCL) exists for reconstituted chalks within the assessed density range, a feature that has not been reported previously. Laser diffraction particle-size analyses and scanning electron microscopy indicate that the ‘uniqueness’ of the NCL may be associated with comparable grain shapes and size distributions, and to grain breakage. These observations underscore the applicability of critical state concepts to describe the mechanical behaviour of reconstituted chalk. The compression paths of intact samples and the NCL for reconstituted chalk define an intact density-controlled structure-permitted space, which is used to estimate macroscopic bond strength. These calculations show that low-density intact chalk is far more reliant on cement bonds than medium density intact chalk to tolerate loading without exhibiting plastic straining. Therefore, the increase in intact strength observed with greater densities appears to result principally from stronger fabric, rather than stronger bonding
DiamondLightSource/gas-hydrate-segmentation-unets: Version 1.0
No full textContains Python code for 2d and 3d U-Net training and prediction along with MATLAB scripts that were used for data preparation tasks and training of RootPainter software
Investigation of pile penetration in calcareous soft rock using X-ray computed tomography
No full textPenetration of open- and closed-ended model piles into intact chalk, a soft calcareous rock, was investigated using microfocus X-ray computed tomography (XCT). Three-dimensional images of the specimens showed that the piles crushed and densified the chalk in their path, creating a crushed chalk annulus around the shaft, a region of compressed destructured chalk below the tip, and fractures across cemented regions of the specimen. Laser-diffraction particle-size analyses of the crushed chalk annulus after exhumation showed limited difference with laboratory-remoulded chalk, which suggested thorough de-cementation. Installation stresses and XCT-derived densities were paired using a simplified cylindrical cavity expansion solution to estimate effective radial stress–void ratio states at the pile tip during penetration. More complex numerical solutions could not be applied using the available data. This approach posed significant problems, as it could not suitably incorporate hardening and non-linear stiffness behaviours of chalk during pile penetration, nor account for the creation of discontinuities. However, effective radial stress–void ratio estimates were found to converge with the reconstituted critical state line of the material at high stresses and low void ratios. This partially supported the use of a critical state framework to characterise pile penetration in chalk, as proposed in recent literature.</p
On Acquisition Parameters and Processing Techniques for Interparticle Contact Detection in Granular Packings Using Synchrotron Computed Tomography
No full textX-ray computed tomography (XCT) is regularly employed in geomechanics to non-destructively measure the solid and pore fractions of soil and rock from reconstructed 3D images. With the increasing availability of high-resolution XCT imaging systems, researchers now seek to measure microfabric parameters such as the number and area of interparticle contacts, which can then be used to inform soil behaviour modelling techniques. However, recent research has evidenced that conventional image processing methods consistently overestimate the number and area of interparticle contacts, mainly due to acquisition-driven image artefacts. The present study seeks to address this issue by systematically assessing the role of XCT acquisition parameters in the accurate detection of interparticle contacts. To this end, synchrotron XCT has been applied to a hexagonal close-packed arrangement of glass pellets with and without a prescribed separation between lattice layers. Different values for the number of projections, exposure time, and rotation range have been evaluated. Conventional global grey value thresholding and novel U-Net segmentation methods have been assessed, followed by local refinements at the presumptive contacts, as per recently proposed contact detection routines. The effect of the different acquisition set-ups and segmentation techniques on contact detection performance is presented and discussed, and optimised workflows are proposed
Application of X-ray μCT to investigate rock-structure interaction on piled foundations for marine aerogenerators
No full textComputed tomography reconstructions of burrow networks for the Opheliid polychaete, Armandia cirrhosa
No full textThe morphology and architecture of structures formed by sediment-dwelling invertebrates, such as excavations or burrows, are often assumed to be characteristic of a given species, consistent across a range of environmental conditions, and used to categorise species contributions to ecosystem functioning. However, very few investigations use non-invasive high-resolution techniques capable of determining fine scale variations in burrow form and complexity, or consider whether or not the form of the burrow is context dependent. Here, we provide replicate high-resolution micro-focus computed tomography data for the complete burrow systems of the Opheliid polychaete, Armandia cirrhosa, across a range of salinity and habitat conditions. These data provide reference models which can be used by ecologists investigating intraspecific variation in species traits and organism-sediment interactions and, more generally, by those tasked with pattern and shape recognition of objects that are morphologically highly variable and which adjust their architecture with changing circumstance or context
Development of a lab-based in situ XCT oven for vacuum-bag processing of prepreg laminates
No full textReal-time 3D microstructure changes in prepreg laminates during curing was observed using widely available X-ray Computed Tomography (XCT) hardware at high temporal resolution (2 min) and spatial resolution (25 µm voxel size). The methodology was demonstrated in a cylindrical convection oven with an internal diameter of 100 mm, a heating rate of 2°C/min, a maximum operating temperature of 135°C, and an integrated vacuum line. The technique was applied to three representative carbon fibre reinforced epoxy prepreg samples having flat, tapered and corner geometries. The increasingly complex geometries lead to higher void mobility and thickness changes that were captured in 40-50 mm size samples. Image processing of the XCT data was enhanced by the use of deep learning semantic segmentation for feature extraction. Uninterrupted microstructure evolution was visualised in larger samples and more realistic processing conditions than previous lab-based In Situ XCT studies.</p
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