Question

done.

Answer 1

@mathmate

Answer 2

I need a reference to the original problem to look at the answers you've got.

For the last paragraph, you need to have the porosity (n) of the soil.
So for each 1 ft^3 of soil there are n ft^3 of voids.
90% saturation would be the weight of 0.90*n ft^3 of water, and so on.

Answer 3

@mathmate i have reposted it up top

Answer 4

@ash90
Thank you for adding the given information, from which I have verified that your answers from (a) to (f) are correct to the number decimal places you provide.
However, in scientific calculations such as what you're doing, it is important to present your answer according to the accuracy provided by the data. If the data are accurate to 3 significant figures, you will need to provide the same accuracy, namely 3 significant digits, in fact four if the number begins with a "1".
In many of your answers, you provided only two significant digits, which
1. does not correspond to the accuracy of data provided, and
2. if used for later calculations, may cause mistakes due to rounding errors.
So for example, I would present the result as
(a) 14.94%,
(b) to (d) are ok as presented
(e) 0.364
(f) 0.687
etc.

For the last part, it is the inverse calculation to part (f).
To find the weight of water to achieve a given degree of saturation, you would start with the definition of degree of saturation = S = Vw/Vv
which gives Vw = S*Vv
From the porosity, n = Vv / Vt, we have Vv = n*Vt
So now Vw = S*n*Vt,
converting to weight,

\(W_w = V_w*62.4 = 62.4~ S~ n~~ \)lbs/ft^3

Given Vt (total volume) = 1 ft^3
S = 100% (saturated), and n=0.364 (porosity),
we have
Ww = 62.4*1.00*0.364*1 = 22.7 lbs
which is the TOTAL amount of water contained in 1 ft^3 of saturated soil.
For the amount of water to be ADDED, you have to subtract what was present initially per cubic foot equal to 3.9*4=15.6 lbs.

You can do a similar calculation for the 90% case.

Answer 5

okay so for 90% saturation i get:
62.4*1.00*0.364*.9=20.4 lbs
20.4/.572=35.7lbs

for 100% saturation iget:
62.4*1.00*0.364*1=22.7lbs
22.7/.572=39.6lbs

is this correct. Sorry for the late response.

Answer 6

hm... not exactly.

porosity=0.36384 means .36384 ft^3 of voids per 1 cubic foot of soil.
If all the voids are filled with water, water will weigh .36384*62.4 lb=22.7 lbs
At 90% saturation, only 90% of the voids would be filled with water, so total amount of water weighs 0.9*22.7=20.4 lbs.
However, the water originally 68.71% saturated, so what you need to add would be (0.9-0.6871)*22.7=4.83 lbs only.

You can proceed similarly for 80% saturation. The answer should be 2.56 lbs.

Post any time if you could use help.

Answer 7

i will if i run into anymore problems. Thanks for the explanation.