In this article, (and video above), we solve a civil engineering soil sample problem to give you a better understanding of what you can expect during the FE Exam.
Question:
A soil sample has a total mass of 24g, a volume of 12cm³, an oven-dry mass of 22g, and a specific gravity of 2.4 for the solids.
The void ratio of this soil sample is most nearly:
Solution:
When we calculate the void ratio of soil samples, we should model the soil as a three phase system of air, water, and solid.
(reference p. 259 in FE Handbook v. 10.1)
In this model:
The volume of solids in the soil is given by the following equation:
Where G is the specific gravity of the solids (given in the problem statement as being 2.4) and ρ_w is the density of water.
The volume of the voids is calculated by finding the difference between the total volume and volume of the solids:
The void ratio is given by the ratio of the volume of the voids divided b the volume of the solids (not the total volume):
Answer:
The correct answer is B
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I hope you found this week’s FE Environmental engineering exam prep question helpful. In upcoming articles, I will answer more FE Exam questions and run through more practice problems. We publish videos bi-weekly on our Pass the FE Exam YouTube Channel. Be sure to visit our page here and click the subscribe button as you’ll get expert tips and tricks – to ensure your best success – that you can’t get anywhere else. Believe me, you won’t want to miss a single video.
Lastly, I encourage you to ask questions in the comments of the videos or here on this page and I’ll read and respond to them in future videos. So, if there’s a specific topic you want me to cover or answer, we have you covered.
I’ll see you next week.
Anthony Fasano, P.E.
Engineering Management Institute
Author of Engineer Your Own Success
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