High-resolution photogrammetry to measure physical aperture of two separated rock fracture surfaces  

作　　者：Masoud Torkan Mateusz Janiszewski Lauri Uotinen Alireza Baghbanan Mikael Rinne 

机构地区：[1]Department of Civil Engineering,Aalto University,Espoo,Finland [2]Department of Mining Engineering,Isfahan University of Technology,Isfahan,Iran

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2024年第8期2922-2934,共13页岩石力学与岩土工程学报（英文版）

基　　金：funding provided by the State Nuclear Waste Management Fund(VYR)and the support of the Ministry of Economic Affairs and Employment of Finland on the Finnish Research Program on Nuclear Waste Management KYT2018 and KYT2022 of the Nuclear Energy Act(990/1987)in the research projects Fluid flow in fractured hard rock mass(RAKKA),funding numbers KYT 1/2021 and KYT 1/2022;Additional support was received from the National Nuclear Safety and Waste Management Research Program SAFER2028,funding numbers SAFER 25/2023(MIRKA)and SAFER 42/2023(CORF).

摘　　要：Photogrammetry,reconstructing three-dimensional(3D)models from overlapping two-dimensional(2D)photos,finds application in rock mechanics and rock engineering to extract geometrical details of reconstructed objects,for example rock fractures.Fracture properties are important for determining the mechanical stability,permeability,strength,and shear behavior of the rock mass.Photogrammetry can be used to reconstruct detailed 3D models of two separated rock fracture surfaces to characterize fracture roughness and physical aperture,which controls the fluid flow,hydromechanical and shear behavior of the rock mass.This research aimed to determine the optimal number of scale bars required to produce high-precision 3D models of a fracture surface.A workflow has been developed to define the physical aperture of a fracture using photogrammetry.Three blocks of Kuru granite(25 cm×25 cm×10 cm)with an artificially induced fracture,were investigated.For scaling 3D models,321 markers were used as ground control points(GCPs)with predefined distances on each block.When the samples were wellmatched in their original positions,the entire block was photographed.Coordinate data of the GCPs were extracted from the 3D model of the blocks.Each half was surveyed separately and georeferenced by GCPs and merged into the same coordinate system.Two fracture surfaces were extracted from the 3D models and the vertical distance between the two surfaces was digitally calculated as physical aperture.Accuracy assessment of the photogrammetric reconstruction showed a 20-30 mm digital control distance accuracy when compared to known distances defined between markers.To attain this accuracy,the study found that at least 200 scale bars were required.Furthermore,photogrammetry was employed to measure changes in aperture under normal stresses.The results obtained from this approach were found to be in good agreement with those obtained using linear variable displacement transducers(LVDTs),with differences ranging from 1 mm to 8μm.

关 键 词：PHOTOGRAMMETRY Physical aperture Rock fracture Predefined distances MARKERS 

分 类 号：TU45[建筑科学—岩土工程]