Experimental Investigation on the Influence of Regional Concrete Spalling on Shield Tunnel Segments

Figure 9

Segment AE test results. (a) Variation curve of acoustic emission for group 1. (b) Variation curve of acoustic emission for group 2. (c) Variation curve of acoustic emission for group 3. (d) Variation curve of acoustic emission for group 4.

(a)

(b)

(c)

(d)