ORCID Profile
0000-0002-8634-1919
Current Organisation
Queen's University
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Publisher: Elsevier BV
Date: 09-1999
Publisher: Elsevier BV
Date: 06-2015
Publisher: Canadian Science Publishing
Date: 05-2016
Abstract: This 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 ex le 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.
Publisher: Thomas Telford Ltd.
Date: 04-2016
Abstract: Relative ground movement represents a severe seismic hazard to pipelines crossing faults, and the maximum expected pipeline strains are the primary design concern. Past research has documented how stiff steel pipelines respond to permanent ground deformation and has produced calibrated empirical models of pipeline response to strike-slip and normal faulting. However, what little data exist on flexible pipelines illustrate how ‘stiff pipeline’ soil reaction models significantly overestimate peak strains for flexible pipelines. Results for four centrifuge tests conducted on model pipelines are presented to quantify the flexural response of pipelines to normal faulting over a wide range of pipeline stiffness. Continuous functions of pipeline and soil displacement calculated using digital image correlation are used to assess pipeline curvature, soil reaction and relative displacement. Comparisons of peak measured curvatures to current design analysis methods confirm that empirical stiff pipeline soil reactions progressively overestimate maximum curvature as the pipeline's stiffness decreases. Two strategies to modify current empirical soil reactions to account for flexible pipelines were then investigated, with the strategy of reducing the stiffness of the empirical soil reaction (while maintaining the advantage of a simplified, abrupt, step-like fault) providing better outcomes than modification to account for more realistic ground displacement profiles.
Publisher: Canadian Science Publishing
Date: 11-2015
Abstract: Centrifuge testing of reduced-scale models has been used to examine the kinematics of jointed pipelines crossing normal ground faults. The model pipeline was fabricated at 1/30th scale using segments of a semicircular cross section cut from an aluminum rod. Threaded rods were used to connect those segments and model a variety of joints having longitudinal bending stiffnesses from 3% to 47% of the bending stiffness of the pipe segments. The semicircular segments were placed against a glass sidewall of the test box and buried in sand. During testing under 30g, differential ground movements of up to 70% of the pipe diameter were imposed, and the pipe movements were monitored using particle image velocimetry. It is shown that maximum rotations occur at the joints when the shear zone generated by the ground fault passes across the joint rather than the pipe segment, and that joint stiffness has little impact on the pipe kinematics. A simplified kinematic model is introduced that permits straightforward, safe estimates of maximum joint rotation.
Publisher: Canadian Science Publishing
Date: 04-2010
DOI: 10.1139/T09-118
Abstract: Three-dimensional ground surface displacements from 20 m long static pipe-bursting experiments are reported. These experiments were conducted with firm-to-stiff clay backfill in a trench with very stiff clay sidewalls at three different burial depths. Multiple digital cameras and image analysis were used to quantify the surface response as the expander progressed through the original pipe. The experiments quantified the upward surface movement as the expander approached, the effect of burial depth on maximum uplift, and the final amount of uplift after it decreased to a residual displacement. The experiments also quantified the axially forward ground surface movement as the expander approached, reaching maximum just ahead of the expander, and decreasing to almost zero after the expander had passed by. Lateral movements of the ground surface away from the centreline are also reported, which were essentially zero at the centre line, increasing to a maximum and then decreasing with distance from the centreline. The three different burial depths produced in effect the same width of vertical surface response with the displacements contained within 1.5 m on either side of the centreline, suggesting that the very stiff clay trench walls had a dominant influence on the measured displacements.
Publisher: Thomas Telford Ltd.
Date: 03-2011
DOI: 10.1680/IJPMG.2011.11.1.23
Abstract: It is a well-established argument that side-wall interface friction can influence the behaviour of soil located at the boundary of physical model test chambers. This effect has a potentially significant influence on measurement techniques such as particle image velocimetry that often rely on images captured at vertical transparent boundaries. However, it is hypothesised that under kinematically controlled boundary conditions, particle image velocimetry can yield not only qualitative but highly accurate quantitative measurements of deformation. In this paper, this hypothesis is tested for the specific soil–structure interaction problem of pipelines being subject to vertical faulting. In the middle of the model, a circular model pipeline was heavily instrumented with 32 pairs of strain gauges. At the same elevation but at the window of the test chamber, an identical model pipeline was split in half axially along its centreline to give a semi-circular cross-section, and placed against the visible window. Three digital cameras were used to record deformations of the pipe and the surrounding soil during the test. After image processing and filtering, measurements of peak curvature obtained from digital image analysis on the half pipeline section are shown to be within 5% of the results obtained from strain gauges.
Publisher: American Society of Civil Engineers (ASCE)
Date: 04-2005
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2009
No related grants have been discovered for W. Andy Take.