00731159

Component

https://doi.org/10.3141/1548-05

http://scholar.google.com...ohoe&publication_year=1996

Laboratory experiments are typically performed on particulate media to study stress-deformation behavior and to verify or calibrate computer models from controlled or measured boundary stresses and displacements. However, such data do not permit the formation of shear bands, displacement fields within flowing granular media, and other small-scale localized deformation phenomena to be identified. Described are two semiautomated computer vision techniques for accurately determining the two-dimensional displacement field in granular soils from video images obtained through a transparent planar viewing window. The techniques described are applicable for studying the behavior of particulate media under plane strain and certain axisymmetric test conditions. Digital image processing and analysis routines are used in two different computer programs, Tracker and Tracer. Tracker uses a graphical user interface that allows individual particles to be selected and tracked through a sequence of digital video images. A contrast edge detection algorithm delineates the two-dimensional projected boundaries of particles. The location of the centroid of each particle selected for tracking is determined from the boundary to quantify the trajectory of each particle. Tracer maps the trace or trajectory of specially dyed fluorescent particles in a sequence of video frames. A thresholding technique segments individual particle trajectories. Together, Tracker and Tracer provide a set of tools for identifying small-scale displacement fields in particulate assemblies deforming under either quasi-static or rapid loading (such as gravity flow).

This paper appears in Transportation Research Record No. 1548, Small-Magnitude Measurements in Geotechnical Engineering.

English

p. 31-37

1996

Transportation Research Record

0309059178

Figures (5) ; References (11) ; Tables (2)

Algorithms; Computer programs; Computer vision; Dislocation (Geology); Granular soils; Image processing; Particles; Sand; Trajectory; User interfaces (Computer science); Vehicle trajectories

Boundaries; Two dimensional; Video images

Geotechnology; Highways; I42: Soil Mechanics

TRIS, TRB

Feb 3 1997 12:00AM

• ANALYSIS OF METHODS USED IN TIME DOMAIN REFLECTOMETRY RESPONSE
• BEHAVIOR OF SHAFT-SAND INTERFACE FROM LOCAL MEASUREMENTS
• CHARACTERIZATION OF GRANULAR SYSTEMS BY DIGITAL SIGNAL PROCESSING OF LOW STRAIN WAVE RESPONSE
• CYCLIC SIMPLE SHEAR APPARATUS FOR LOW-STRAIN SOIL TESTS
• DEVELOPMENT OF CYCLIC TRIAXIAL APPARATUS WITH BROAD FREQUENCY AND STRAIN RANGES
• DISPLACEMENT DURING PROGRESSIVE FAILURE ESTIMATED FROM MICROSEISMIC ACTIVITY
• INSTRUMENTATION FOR LATERALLY LOADED MODEL PILES
• LOW STRAIN DYNAMIC SHEAR MODULUS OF CEMENTED SAND FROM CONE PENETRATION TEST RESULTS
• MEASUREMENT OF SOIL RESILIENT PROPERTIES USING NONCONTACTING PROXIMITY SENSORS
• RADIAL STRAIN MEASUREMENTS IN RESONANT COLUMN AND TORSIONAL SHEAR TESTS
• SMALL- AND HIGH-STRAIN MEASUREMENTS OF IN SITU SOIL PROPERTIES USING THE SEISMIC CONE PENETROMETER
• SOIL PARTICLE SIZE ANALYSIS USING X-RAY ABSORPTION