Internal Photogrammetry System for 3-D Measurements of Triaxial Soil Samples


The triaxial test, a standard test for measuring soil shear strength, is critical to the design of foundations for all structures founded on soil, such as bridges or buildings. Currently, the cross-sectional area of a triaxial soil sample is assumed during testing, which may lead to strength measurement errors of up to 30%. The device overcomes this error by accurately determining the failure plane of the sample. Furthermore, the internal camera system allows for three-dimensional tracking of hundreds of individual targets on the surface of a sample. Targets are located to within 0.01-mm of their actual location in x-y-z coordinates, allowing for accurate characterization of local deformations on the sample surface. Targets are used to reconstruct three-dimensional models of samples, thereby allowing for measurement of total volumetric changes to within +-0.3% of the actual volume of a sample.


The novel invention, capable of making these measurements, allows for:


1) unobstructed, non-contacting, and non-destructive monitoring of a soil sample within the triaxial testing apparatus during all stages of testing


2) capture of digital images and video of a soil sample during all stages of testing, and


3) three-dimensional modeling of a soil sample at any given stage of testing by using the principles of photogrammetry. 


The new system has been shown to provide accurate measurements of soil specimen dimensions, cross-sectional area, level of strain, volume, and failure plane angle as a function of time. The internal system reduces the overall computational effort required for the development of three-dimensional models of soil samples by eliminating many of the required corrections. Currently, there is no reliable alternative for monitoring soil samples during testing.


The new system is patent-pending and is available for license.


Patent Information:
App Type Country Serial No. Patent No. File Date Issued Date Expire Date
Provisional United States 62/259,397 11/24/2015    
Non-Provisional United States 15/360,820 11/23/2016    
For Information, Contact:
Mark Swaney
Technology Licensing Officer
University of Arkansas
Richard Coffman
Sean Salazar
© 2018. All Rights Reserved. Powered by Inteum