Date of Graduation
Bachelor of Science
Richard A. Coffman PhD PE PLS
Kevin D. Hall PhD
Michelle L. Bernhardt PhD
Accurate strain and volume measurements are critical to phase relationships and strength determination for saturated and unsaturated soils. In recent years, laboratory-based photographic techniques of monitoring soil specimens have become more common. These techniques have been used to reconstruct 3D models and to determine strain and volumetric changes of triaxial specimens. A new technique that utilized digital photographs of the soil specimen, captured from within a triaxial testing cell, was utilized. Photographs were processed using photogrammetry software to reconstruct 3D models of the soil specimens. By placing camera equipment within the cell, the technique eliminated the need to account for optical distortions due to 1) refraction at the confining fluid-cell wall-atmosphere interface, 2) the curvature of the cylindrical cell wall, and 3) the pressure-induced deformation of the cell wall.
As documented herein, the internal photogrammetry approach was validated using analog specimens and triaxial compression and extension tests. Furthermore, the viability of determining total and local strains, volume changes, and total volume at any given stage of testing was evaluated. By comparison with other volume-determination methods, including DSLR camera photogrammetry, 3D scanning, manual measurements and water displacement techniques, an accuracy of the internal photogrammetry technique of 0.13 percent was assessed.
Miramontes, Leah D., "Validation of an Internal Camera Based Volume Determination System for Triaxial Testing" (2016). Civil Engineering Undergraduate Honors Theses. 33.