NCEES problem 107

[PEin2010]

Can someone break down this problem for me - NCEES problem #107?

I understand what they have done in the solution to arrive at the answer of ©, but I would really appreciate it if someone can break down the thought process to me, in case of a similar problem in the exam.

a water content is given, dry densities of borrow pit and compacted soil are given...I was trying to build the table of mass-volume relations and it was taking me much longer and I still didn't arrive at the correct answer. The way they have solved it seems to be much simpler.

Thanks.

 

[littlebig]

Good question. I forgot exactly how the question is asked. But don't use the mass diagram on this. Just use the 3 phase relationship of soil, for the borrow pit and fill. Hope it helps.

 

[chess5329]

Good question. I forgot exactly how the question is asked. But don't use the mass diagram on this. Just use the 3 phase relationship of soil, for the borrow pit and fill. Hope it helps.

See if this helps:

Always separate the control volume and the Borrow volume:

Borrow site volume: Dry density=116 lb/ft3 and has 14% of optimum water content so, this is the optimum moisture that we want in the construction embankment but, when you hauling to the site the soil arrives with only 9% of moisture so you have to add the other 5% of water to make it optimum.

Control Volume is the 500,000 yd3 of compacted soil with a MDD=90% and has to be with a w=14%, so far we have:

500,000 yd3=13,500,00 ft3(116)(.90)(.05)=70,470,000 lb (1 gal/8.33 lb)=8,460,000 gal of water that you need to add. answear C)

I hope this help you!