China on highest flood alert as 38m people evacuated

asia.nikkei.com ^ | 7/13/2020 | CK TAN, Nikkei staff writer

[petitfour]

Is the WuFlu over in China?????????????

[shotgun]

By my math:

1 foot of head of water is equal to 0.433 psi.

200 feet of head x .433 psi/ft of head = 86.6 psi

Using 200 feet height x 8,000 feet long x 144 inches/sf = 230,400,000 square inches of surface area.

230,400,000 sq. inches x 86.6 PSI = 19,952,640,000 lbs

19,952,640,000 lbs / 2,000 lbs/ton = 9,976,320 tons

Therefore if the resistance capacity of the dam is 25 million tons, then there is a safety factor of 2.5

[palmer]

Thanks, those seem like reasonable numbers except I might cut the head in half instead of the full height of the dam snice you are using the full area. It speaks to the possibility of complete failure.

What I am also considering is the possibilitiy of failure in some section with defective design or installation. Then some water breaks through and starts eating away at the opening. How long the rest holds up is an open question but it will throttle the flow as long as it holds up.

Either way, we'll have lots of video to study.

[shotgun]

The fault would have to span nearly the entire width of the dam from face to the back. Enough so that the pressure of the water would cause the fault to exoand until complete failure.

Once open the water would pour out and scour velocity would be enough to erode the exposed concrete. Imperfections in the compaction of the concrete when it was poured would cause the oowning to continue enlarging allowing more water to flow out. Similarly, the water pressure on the earthen ends of the dam could also be another point of weakness.