Volume 33, Issue 4 (July 2010) Spatial Deformation Measurement
Using Transparent Soil This paper addresses the need for
nonintrusively measuring spatial deformation pattern inside
soils. In this study, transparent soil surrogates are used in
model tests instead of natural soils. Transparent soil with
macrogeotechnical properties similar to those of natural soils
was made of either transparent amorphous silica gels or powders
and a pore fluid with a matching refractive index. An optical
system consisting of a laser light, a line-generator lens, a
charge-coupled device (CCD) camera, a frame grabber, and a
computer was developed to optically slice a transparent soil
model. A distinctive speckle pattern is generated by the
interaction of the laser light and transparent soil. The laser
speckle images before and after deformation were used to
nonintrusively measure the relative displacement field using
digital image cross-correlation. Spatial displacement fields
under a model footing were obtained by combining seve