01697985

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Conventional methods for measuring the deformational response of geosynthetics, such as linear variable differential transformer (LVDT), strain gauges, and extensometers have several limitations in fully determining the complete strain distribution in geosynthetics. Recently, an image-based method which has many advantages over existing methods has been proposed to measure the deformational properties of geosynthetics. However, this method requires accurate manual control of camera position and assumes that the geosynthetics remains planar during the whole testing process. Both of the requirements cannot be satisfied for several reasons, and thus lead to misleading results. To overcome the limitations of existing methods, this paper presents a photogrammetric method which can accurately measure the 3D full field displacements of geosynthetics during tensile tests. Tensile test on a geogrid specimen was performed to verify the effectiveness and accuracy of the proposed photogrammetric method. The proposed method is non-contact, cost-effective, highly accurate, capable of measuring 3D deformation of geosynthetics and identifying localized strain. It is shown that the average absolute difference in displacement obtained by the machine and the proposed photogrammetric method is 0.25%, and the average absolute error is 0.038 mm. 3D deformation analysis shows that the R-squared of fitting planes of the geogrids is initially 97.2%, and can decrease to 95.2% during the tensile tests. The proposed photogrammetric method also demonstrates that the manual control of camera positions and shooting direction is impossible, and the proposed method does not require the camera positions and shooting direction to be controlled.

This paper was sponsored by TRB committee AFB80 Standing Committee on Geospatial Data Acquisition Technologies.

19-05112

English

28p

2019

Transportation Research Board 98th Annual Meeting

Digital/other

Figures; Photos; References; Tables

Dislocation (Geology); Geosynthetics; Image analysis; Photogrammetry; Tension tests

Geotechnology; Highways; Materials

Transportation Research Board Annual Meeting 2019 Paper #19-05112

TRIS, TRB, ATRI

Dec 7 2018 9:43AM