New image analysis-based displacement-measurement system for geotechnical centrifuge modeling tests

Centrifuge modeling is widely used in geotechnical engineering. A measurement system termed “GIAS-c” (GeoImage Analysis System for centrifuge) was developed to measure the displacement field of soil using correlation-based image analysis during geotechnical centrifuge model tests. Using this system, a large number of high-quality images with high resolution and frame-rate can be captured and saved to the hard disk via the memory of a computer placed in the centrifuge machine. An image-correlation algorithm was used to determine the displacement vectors of soil without disturbance of the soil itself. The image-acquisition and displacement measurement are fully controlled using this system. The displacement history of an arbitrary point within the soil surface can be measured with sub-pixel accuracy and visualized graphically. The measurement results of a centrifuge model test of the failure process of a soil slope show that the failure process is strongly dependent on the locations and development of several types of strain localization. Shear deformation of the slope was concentrated in a narrow band with an estimated thickness of 6–8 mm, which can be regarded as the characteristic size of the shear band.