PSI - Issue 37

Koji Uenishi et al. / Procedia Structural Integrity 37 (2022) 404–409 Uenishi and Xi / Structural Integrity Procedia 00 (2022) 000 – 000

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from a height of about 900 mm, which theoretically gives an impact velocity of 4.2 m/s. The face as well as the left lower surface of the slope is reinforced with an additional solid plate that serves as a retaining wall. In the experimentally obtained isochromatic fringe patterns (Fig. 3(a)) as well as in the pictures showing difference of colors between the snapshots before and after the dynamic impact (Fig. 3(b)), besides the downward unidirectional stress transfer akin to Fig. 2 top, another stress transfer along the top horizontal free surface is visible. This horizontal stress transfer moves towards the retaining wall and then extends along the slope face (Fig. 3(b)). The confining retaining wall protects the slope from total collapse but at the same time causes buckling-like jump of the particles on the top free surface (Fig. 3(a)). Similar mechanical effect can be observed in a granular slope with a vertical face that is reinforced with a vertical solid retaining wall.

a

b

10 mm

Retaining wall

Steel ball

Stress transfer

Stress transfer

Buckling-like jump

Stress transfer

Stress transfer

Fig. 3. Now the slope face is confined by a retaining wall made of polycarbonate and the top surface is subjected to dynamic impact by a free falling steel ball (sphere of diameter 15 mm, mass 0.2 grams, impact velocity 4.2 m/s). Again, experimentally taken isochromatic fringe patterns (a) as well as difference of colors between the photographs before and after the dynamic impact (b) is shown. The time elapsed after the topmost snapshot is (a) 400, 4000 and 8000  s and (b) 100, 200 and 300  s, respectively.