Optical Characterization of Intrinsic Properties and Fabric of Coarse-Grained Soils

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

This research project aims to bring intrinsic soil properties including particle shape, angularity and surface roughness as well as soil fabric into wider common practice and research through development of optical methods for rapidly quantifying them at no extra time or cost than required to develop grain size distributions. To accomplish this, a sediment imaging (Sedimaging) system will be used for particles smaller than 2 mm and a translucent segregation table (TST) will be used for the coarser fraction. Both systems rapidly sort a statistically representative soil specimen prior to image capture. Most importantly, although the particles are sorted, they need not be separated from contact with each other. This allows for a large number of particles to be rapidly evaluated. Furthermore, because of the recent introduction of high resolution cameras approaching 40 MPix, only one high resolution photograph is needed in each test. The major research tasks include: development of advanced Sedimaging and TST systems; segmentation of particles from images of 3D assemblies and selection of segmented particles for shape analysis; quantification of particle shape of segmented particles; comparison of particle Roundness and Sphericity obtained from Sedimaging and TST images with traditionally obtained (ex-situ) measures; determination of typical shape distributions as a function of particle size within specimens; establishing minimum particle size for which shape descriptors should be determined; evaluation of surface roughness by corner detection methods; development of a wavelet-based index for soil fabric potential; performance of laboratory tests for confirmation of previous findings on particle shape and fabric effects; and extension of methods to images collected in-situ by the vision cone penetrometer. Broader impacts will be addressed on three distinct fronts. First, the Sedimaging and TST tests will become regular and distinct laboratory exercises in the undergraduate Introductory Geotechnical Engineering course at the University of Michigan. This will demonstrate that research findings and developments do transfer into engineering practice. Secondly, working with the University of Michigan Ergonomics Research Center and three local sand and aggregate producers, the geotechnical laboratory work environment will be evaluated with emphasis on improvements created by the Sedimaging and TST systems that relieve workers from the tedium of particle size and aspect ratio testing. Finally, the impediments to technology transfer (from research to practice) in geotechnical and geoenvironmental engineering will be investigated and documented by geotechnical specialty area (i.e soil improvement, deep foundations, retaining structures, etc.).