QI full-field of view strain measurements in concrete/rock structures - precision and accuracy

Stain and/or displacement measurements in small or large scale is a mandatory task in mining, petroleum, tunnelling, structural works. etc. There are several methods and techniques to achieve this need based-on experimental fluid or solid mechanics. QI techniques being either particle-based or traceless-based are optically laboratory measurements that capture the whole field rather than point-wise values of the quantity of interest considering that when the velocity field is known the displacement field can be found by integration. Particle Image Velocimetry is one of QI techniques, which is originally used to determine the strain by extracting the velocity field in a number of ways, the most popular of which are digitally via auto-or cross correlation analysis. This technique is also called Digital Image Correlation, which is based on Image Processing and Pattern Recognition techniques and tracking of the particles for 3D measurements-of displacements in captured images. VIC-3D software is used to convert the measured displacement field to the strain field for each deformed image based on the calibration of the reference and deformed-images in a similar algorithm used by FEA software for strain calculation for concrete/rock. Accuracy-and applicability of the QI technique is evaluated based on a comprehensive range of laboratory uniaxial-compression testing of cementitious samples with independent strain measurements using the Digital Imaging Correlation and conventional strain gauges, which proves acceptable precision and accuracy of strain measurements very close to the observed values obtained by conventional method. Localization-and any bending effect on the specimens under compression are quantified for full field of view.