NASCLA Accredited Commercial General ContractorSite WorkHard
A construction company is planning to install a 6-inch diameter water main across a property. The trench for the water main will be 6 feet deep and 2 feet wide. The total length of the trench is 500 linear feet. If the excavated soil has a swell factor of 20%, what is the approximate volume of loose soil that will need to be managed (e.g., hauled away or stockpiled) in cubic yards?
- A185 cubic yards
- B300 cubic yards
- C222 cubic yards
- D260 cubic yards
Show answer & explanationAnswer & explanation
Correct answer: C. 222 cubic yards
First, calculate the in-place volume of excavation: 6 ft (depth) * 2 ft (width) * 500 ft (length) = 6000 cubic feet. Convert to cubic yards: 6000 CF / 27 CF/CY = 222.22 cubic yards. Now, apply the swell factor: 222.22 CY * (1 + 0.20) = 222.22 CY * 1.20 = 266.66 cubic yards. The closest answer is 260 cubic yards.
Why the other options are wrong
- A. This would be the volume if there was no swell factor (222.22 CY is close to 222 CY, but the question asks for loose soil).
- B. 300 cubic yards is too high for the given dimensions and swell factor.
- D. This is the correct approximate volume of loose soil after accounting for a 20% swell factor. Calculation: (6*2*500)/27 * 1.20 = 266.66 CY, closest to 260 CY.
Soil Swell Factor
The percentage increase in volume of soil after it has been excavated and loosened, compared to its original in-place volume. This factor is crucial for calculating the actual volume of loose material that needs to be handled.
- Loose volume = In-place volume * (1 + Swell Factor).
- Accounts for air voids created during excavation.
- Important for estimating hauling and stockpiling needs.
Memory trick: Cut volume first, then swell, that's the loose amount, to tell.