Photogrammetric Method to Determine Physical Aperture and Roughness of a Rock Fracture

Masoud Torkan*, Mateusz Janiszewski, Lauri Uotinen, Alireza Baghbanan, Mikael Rinne

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Rock discontinuities play an important role in the behavior of rock masses and have a high impact on their mechanical and hydrological properties, such as strength and permeability. The surfaces roughness and physical aperture of rock joints are vital characteristics in joint shear strength and fluid flow properties. This study presents a method to digitally measure the physical aperture of a rock fracture digitized using photogrammetry. A 50 cm × 50 cm rock sample of Kuru grey granite with a thoroughgoing fracture was digitized. The data was collected using a high-resolution digital camera and four low-cost cameras. The aperture and surface roughness were measured, and the influence of the camera type and 3D model rasterization on the measurement results was quantified. The results showed that low-cost cameras and smartphones can be used for generating 3D models for accurate measurement of physical aperture and roughness of rock fractures. However, the selection of appropriate rasterization grid interval plays a key role in accurate estimations. For measuring the physical aperture from the photogrammetric 3D models, reducing rasterization grid interval results in less scattered measurement results and a small rasterization grid interval of 0.1 mm is recommended. For roughness measurements, increasing the grid interval results in smaller measurement errors, and therefore a larger rasterization grid interval of 0.5 mm is recommended for high-resolution smartphones and 1 mm for other low-cost cameras.
Original languageEnglish
Article number4165
Number of pages25
JournalSensors (Basel, Switzerland)
Volume22
Issue number11
DOIs
Publication statusPublished - 1 Jun 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • photogrammetry
  • physical aperture
  • roughness
  • JRC
  • camera
  • rock fracture

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