Cofferdams (suspended solids question)

[VoyageofDiscovery]

Does anyone know how to calculate the relative density (specific gravity) of water with 40,000 ppm of suspended solids (fine silts).

This is not structural question, but I would assume structural engineers that design cofferdams in rivers may have encountered this before.

VOD

 

[JedClampett]

Try (40,000/1,000,000(150 pcf)+ 960,000/1,000,000(62.5 pcf))/62.5 pcf.

 

[Focht3]

JedClampett got you pretty close. He used a specific gravity of 2.4 for the silts (150/62.4). The specific gravity is closer to 2.7.

The corrected equation is:

40000/1000000*(62.4*2.7)+960000/1000000*(62.4)

which yields a value of almost 67 pcf. That's pretty thick stuff.

(The equation above can be copied straight into Excel.)

 

[VoyageofDiscovery]

Outdone again

Regards

VOD

 

[fuchsjr]

You could use a cheap hydrometer with a sample of the material.

 

[Focht3]

Yeah, but calculating it is so much fun!