1,720,983 research outputs found
Discussion on "Application of Particle Image Velocimetry (PIV) in Centrifuge Testing of Uniform Clay"
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Soil deformation measurement using particle image velocimetry (PIV) and photogrammetry
No full textA deformation measurement system based on particle image velocimetry (PIV) and close-range photogrammetry has been developed for use in geotechnical testing. In this paper, the theory underlying this system is described, and the performance is validated. Digital photography is used to capture images of planar soil deformation. Using PIV, the movement of a fine mesh of soil patches is measured to a high precision. Since PIV operates on the image texture, intrusive target markers need not be installed in the observed soil. The resulting displacement vectors are converted from image space to object space using a photogrammetric transformation. A series of validation experiments are reported. These demonstrate that the precision, accuracy and resolution of the system are an order of magnitude higher than previous image-based deformation methods, and are comparable to local instrumentation used in element testing. This performance is achieved concurrent with an order of magnitude increase in the number of measurement points that can be fitted in an image. The performance of the system is illustrated with two example applications.</p
General report for TC104 physical modelling in geotechnics
No full textThe session of the 18th ICSMGE on physical modelling in geotechnics, held by Technical Committee 104, provides an opportunity to reflect on the varied contributions that physical modelling makes to our profession - in both research and practice. The 27 papers contributed within this theme span many different applications of physical modelling. These range from simple small-scale laboratory tests to reveal mechanisms of soil-structure interaction - particularly where simulation by numerical methods is problematic -Through to scaled-down versions of field constructions, performed outdoors, to validate the performance of new monitoring technology. These examples show physical modelling in action across the entire spectrum of geotechnics, from the validation of fundamental analysis principles, to the assurance of construction technology. In all cases, physical models - defined here as physical idealisations of all or part of an envisioned geotechnical system - provide a more convenient method of gaining knowledge than observing or simulating the full geotechnical system.</p
A deformation measurement system for geotechnical testing based on digital imaging, close-range photogrammetry, and PIV image analysis
No full textImproved image-based deformation measurement for geotechnical applications
Full text linkThis paper describes and benchmarks a new implementation of image-based deformation measurement for geotechnical applications. The updated approach combines a range of advances in image analysis algorithms and techniques best suited to geotechnical applications. Performance benchmarking of the new approach has used a series of artificial images subjected to prescribed spatially varying displacement fields. An improvement by at least a factor of 10 in measurement precision is achieved relative to the most commonly used particle image velocimetry (PIV) approach for all deformation modes, including rigid-body displacements, rotations, and strains (compressive and shear). Lastly, an example analysis of a centrifuge model test is used to demonstrate the capabilities of the new approach. The strain field generated by penetration of a flat footing and an entrapped sand plug into an underlying clay layer is computed and compared for both the current and updated algorithms. This analysis demonstrates that the enhanced measurement precision improves the clarity of the interpretation.</p
Remote real-time monitoring of tunnelling-induced settlement using image analysis
No full textA new image-based deformation measurement technique has been developed for real-time monitoring of construction settlements. This development combines the technologies of remote digital photography, automated file transfer, the image processing technique of Particle Image Velocimetry (PIV), and a web-based reporting system. This paper describes the technology behind this new development and presents key observations from its application to the monitoring of tunnelling-induced settlements of a retaining wall in real-time as construction progressed. Additional data is presented from a validation exercise in which the performance of the technique is shown to be comparable to conventional surveying techniques.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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