**3.2. Digital image analysis**

In order to evaluate the displacement of the gauge points, the digital image analysis method used in the 1-G shaking table test [2] is applied.

Firstly, the static image is taken before the model is tested. While the model is excited, continuous images are taken by the high-speed camera of which the shooting speed is 1000 fps. The images are transformed into black and white binary images. The noise reduction is, then, carried out as shown in **Figure 6**. The number of the points is confirmed to be 82 at this stage. Then, the coordinates of the gauge points are measured in the unit of pixels by calculating the center position of each white element representing the gauge point. Finally, the distance between two reference points at the foundation, which was precisely 150 mm, is measured in the unit of pixels. The scale calibration is carried out by the distance of reference points and the coordinate of the gauge points is calculated as the relative location of the reference point in the unit of mm. By repeating this procedure for all dynamic images, the displacement variation of each gauge point can be obtained.

**Figure 5.** Particle size distribution used for the embankment model.

**Figure 4.** Schematic view of the model and soil box for centrifugal loading test. (a) Schematic view of the model; and (b)

image analysis, the behavior of cross section was observed. It was found that the share stain became large at the slope, and the large volumetric strain was observed at the upper part of the

The centrifugal loading tests were conducted under 50-G with a 1/50 scaled model. In this experiment, the model with a height of 100 mm and upstream and downstream gradients of 1:1 was used. **Figure 4** shows the schematic view of the model. The model was made from

dam. In this study, a similar image analysis is used for the centrifugal loading test.

**3. Centrifugal loading test**

**3.1. Test conditions**

26 Dam Engineering

the situation of soil box for centrifugal loading test.

**Figure 6.** Examples of image analysis process: (a) picture image; (b) binary image; and (c) noise reduction result.
