A Least Square Optimization Approach for Determining the Soil Boundary and Absolute Volume of Unsaturated Soils


Triaxial tests have been widely used for evaluating the stress-strain behavior of both saturated and unsaturated soils, in which, the volume measurement is a very important component; however, existing methods can only measure relative volume changes during triaxial testing. Recently a photogrammetry-based method has been proposed to measure volume changes of both saturated and unsaturated soil. Although this method has many advantages over conventional methods, it still has one drawback: the incapability to determine the top and bottom boundaries of the soil sample in the triaxial testing. In order to overcome this limitation, a least-square optimization approach and 3D reconstruction of triaxial testing were performed using the photogrammetry-based method. Many validation tests have been performed to calculate the distance between the top and bottom boundaries that confirmed the accuracy of the proposed method. This proposed method demonstrated very high accuracy by comparing the results and the measured distance with a difference of 0.0807 mm.

Meeting Name

Geo-Congress 2020: Modeling, Geomaterials, and Site Characterization (2020: Feb. 25-28, Minneapolis, MN)


Civil, Architectural and Environmental Engineering

Research Center/Lab(s)

Center for Research in Energy and Environment (CREE)

Keywords and Phrases

Least Squares Approximations; Photogrammetry; Soil Mechanics; Soil Surveys; Soils, 3D Reconstruction; Conventional Methods; Least Square Optimization; Saturated and Unsaturated Soils; Stress-Strain Behaviors; Triaxial Testing; Unsaturated Soil; Validation Test, Soil Testing

International Standard Serial Number (ISSN)


Document Type

Article - Conference proceedings

Document Version


File Type





© 2020 American Society of Civil Engineers (ASCE), All rights reserved.

Publication Date

01 Feb 2020