Wikipedia
Structural integrity
A number of concerns have arisen about the possibly inadequate structural stability of the dam itself. Several days after the first filling of the reservoir, around 80 visible cracks were observed in the dam’s structure.[91][92] The cracks were described to be “hairline” despite their size and depth.[93] The submerged spillway gates of the dam pose a risk of cavitation,[94] which is similar to the cavitation that destroyed the spillways of the Glen Canyon Dam in the floods of 1983.
The Three Gorges Dam Project Corporation responded to the criticism of the dam integrity, saying that the project quality is under control over its 17 years of construction. Around 163,000 concrete units of the dam all passed the quality test. After filling of the reservoir, the dam deformation was within the design limit. The right side of the dam is free of cracks, which is a significant achievement of the project. An experts group gave the project overall a good rating in terms of quality
China: cracks in the Three Gorges Dam, so 300,000 people can wave goodbye to their homes
This does bring up a concern. Quality control is not one of Chinese products strong points.