Photogrammetry for characterizing rock fracture roughness, physical aperture, and hydromechanical properties

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School of Engineering | Doctoral thesis (article-based) | Defence date: 2024-10-11
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Date

2024

Department

Rakennustekniikan laitos
Department of Civil Engineering

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Mcode

Degree programme

Language

en

Pages

75 + app. 117

Series

Aalto University publication series DOCTORAL THESES, 191/2024

Abstract

Understanding rock mass behavior is vital for various applications, including nuclear waste disposal and civil projects. Geometrical properties of single rock fractures, like roughness and physical aperture, significantly affect shear strength and fluid flow. This research aimed to characterize single rock fracture properties such as roughness, physical aperture, or hydromechanical attributes using photogrammetry of Kuru granite. Push shear tests were conducted on two sample sizes (200 cm × 100 cm and 50 cm × 25 cm), revealing a reduction of peak shear strength and friction angle for the larger size. Roughness back-calculated from shear tests for the larger sample was lower than the estimates from profilometer or photogrammetry. Scale adjustment was necessary for the correction of roughness estimation for the larger sample. Experimental differences may also stem from matedness. Using low-cost cameras in photogrammetry was investigated for a sample size of 50 cm × 50 cm. While smartphones show promise, caution is advised due to potential accuracy issues. Notably, the sampling intervals of 3D point clouds could affect roughness and physical aperture measurement results. A high-precision photogrammetric method was developed for measuring the physical aperture of three 25 cm × 25 cm samples. Markers at predefined distances used as scale bars were attached to each sample. The Root Mean Square Error (RMSE) between actual and calculated distances ranged from 20 to 30 µm. This method showed high accuracy compared to linear variable displacement transducers (LVDTs) for measuring fracture closure under normal stresses (0, 0.1, 0.3, and 0.5 MPa), with differences ranging from 1 to 8 µm. Achieving this level of accuracy required using at least 200 scale bars. Hydromechanical tests were conducted with fluid pressure gradients from 20 to 200 kPa/m and under the abovementioned normal stresses. The relationship between fluid pressure gradient and flow rate followed the nonlinear Forchheimer equation. Roughness displayed anisotropy, with greater roughness resulting in lower conductivity. Simulations were performed under different conditions and compared with laboratory fluid flow tests for validation. Scale effects study revealed significant variations in roughness and permeability with sample size changes. Three 100 cm × 100 cm surfaces were extracted from the 3D model of the bottom half of the 200 cm × 100 cm sample. Then, square subsample sizes ranging from 5 to 100 cm were extracted to estimate roughness and permeability. The surfaces were duplicated and shifted 350 µm to match the initial physical aperture of the 25 cm × 25 cm samples. Square subsample sizes below 30 cm showed variations in roughness and permeability, while these properties tended to be relatively stable states beyond this sample size. In conclusion, the study showed the feasibility of using photogrammetry to accurately characterize different rough fracture sizes for different applications.

Description

Supervising professor

Rinne, Mikael, Prof., Aalto University, Department of Civil Engineering, Finland

Thesis advisor

Uotinen, Lauri, Staff Scientist, Aalto University, Department of Civil Engineering, Finland
Baghbanan, Alireza, Prof., Isfahan University of Technology, Iran

Keywords

photogrammetry, fracture, roughness, physical aperture, camera, fluid flow, accuracy, scale effect

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Parts

  • [Publication 1]: Uotinen, Lauri; Torkan, Masoud; Baghbanan, Alireza; Caballero Hernández, Enrique; Rinne, Mikael. 2021. Photogrammetric prediction of rock fracture properties and validation with metric shear tests. MDPI AG. Geosciences, volume 11, issue 22, article number 293. ISSN 2076-3263 (online).
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202108118308
    DOI: 10.3390/geosciences11070293 View at publisher
  • [Publication 2]: Torkan, Masoud; Janiszewski, Mateusz; Uotinen, Lauri; Baghbanan, Alireza; Rinne, Mikael. 2022. Photogrammetric Method to Determine Physical Aperture and Roughness of a Rock Fracture. MDPI AG. Sensors, volume 22, issue 11, article number 4165. ISSN 1424-8220 (online).
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202206083634
    DOI: 10.3390/s22114165 View at publisher
  • [Publication 3]: Torkan, Masoud; Janiszewski, Mateusz; Uotinen, Lauri; Baghbanan, Alireza; Rinne, Mikael. 2023. High-resolution photogrammetry to measure physical aperture of two separated rock fracture surfaces. Journal of Rock Mechanics and Geotechnical Engineering.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202409046184
    DOI: 10.1016/j.jrmge.2023.10.003 View at publisher
  • [Publication 4]: Torkan, Masoud; Uotinen, Lauri; Baghbanan, Alireza; Rinne, Mikael. 2024. Experimental and numerical characterization of hydro-mechanical properties of rock fractures: the effect of the sample size on roughness and hydraulic aperture. Submitted manuscript to the journal of International Journal of Rock Mechanics and Mining Sciences

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Permanent link to this item

https://urn.fi/URN:ISBN:978-952-64-2019-6

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