Expert Advice 2

[polar888]

I'm a construction management student. When it comes to grading and excavation, I am unable to research a clear and easy definition of "load factor" in reference to shrinkage and sewage. I have the numbers in the chart from the homework, but what is this 'factor' actually telling me?

Thank you,
Damon

 

[Ron]

I'm unclear about your reference to sewage. Please clarify. Are you looking for an explanation of "load factors" as related to volume and density changes when you excavate, haul, fill and compact soil?

 

[msquared48]

Probably correct for the cut - fill volume factors Ron.

Just a guess, but the Sewage load factor could involve such factors as the percentage of particulate matter, BOD, or other factors such as dissolved nitrogen...

Mike McCann, PE, SE (WA)

 

[coloeng]

Maybe he meant to say "waste" instead of "sewage".

 

[polar888]

My apologies for the typo. I meant shrinkage and swellage, not sewage. I am confused at what a Load Factor is. I understand dirt in-situ is at 1. Then, when dug up and placed into trucks, it swells and now, for example become 1.3. Then, when it is compacted, it might be .85. Compaction is a direct result of effort, not a natural state. I don't understand what the Load Factor is or what it is telling me.

 

[Ron]

The load factor is a ratio of unit weights from the "bank" condition to the loose or excavated condition. For your purposes, it is the loose condition unit weight divided by the in situ unit weight.

 

[EireChch]

The factors as I understand them is that if you excavate material and have to excavate it off site expands. for example if you excavate 100 cubes you will need enough trucks to cart off 130 cubes (i.e. 100x1.3).

 

[HockeyPuck]

I actually keep a printed hard copy of this exhibit in my crib book, found it years ago, it is the best explanation of shrink & swell I've found. I think pages 3-6 will help you.

In any shrink & swell calculations I run, I use a 35% factor for swell and a 15% shrinkage.

http://www.ce.udel.edu/courses/CIEG 486/earthworks_notes.pdf