Earthwork: Estimating Utilities

[usaedy]

Just wanted to get some input as to the methods others use to estimate volumes of dirt from utility trenches. I am only interested in pipe spoils really, what is remaining after excavation and backfill.

I am an Agtek User and find it I can't get a final volume using earthwork 3D. I can calc the whole trench volume, but it takes a lot of work. Materials 3D will probably do the job if proper set up is done. But you can't apply swell factors or map the strata in that program. I am not currently using that program to the best of it's aility.

What methods do you use to determine pipe spoils on a project when dealing with over all site balance? Is there an easier way than determining linear footage by hand calc's and applying the trench cross sectional area?

If you're an Agtek user, how are you using earthwork 3D to determine final trench spoils?

Any input would be great.

 

[cvg]

yes, calculate pipe cross sectional area (using outside diameter). Add for any bedding which is imported. multiply times the length. Adjust for shrink/swell and The rest of the dirt should fit back in the trench

 

[Dozerman56]

In terms of the grading balance of a site, I don't think it's possible to calculate a meaningful value for the effect of pipe spoils. Too much variability in topography, shrink/swell assumptions and stripping and reuse of topsoil. But if you create a new surface with the inverts of your lines entered as sloping lines, you can use offsets to create your trench template and calculate the excavated volume.

 

[usaedy]

You are right dozerman. I was trained to do it that way. That method is great for an excavating company, when you have to know the total amount of dirt moved for cost estimates, but I am a builder and am using Agtek to evaluate plans for total site balance. Additional pipe spoils can add upwards of 20,000 c.y. of spoils to the over all balance. When you have to move dirt offsite at $5/yard or more, that's $100,000 in savings if you can calc it upfront and raise the site to accomodate.

Agtek has fallen behind the technology, unfortunately. It looks like insite (

http://www.insitesoftware.com/)

has added that functionality to their software. I hope Agtek will catch up!!!! It will make takeoffs soooo much nicer and much more accurate.

 

[Dozerman56]

Apparently I'm not following you. If you calculate your total trench excavation from design subgrade, your spoils are going to be the volume of the pipe and the bedding, minus whatever shrinkage you put onto your backfill. So
your spoils should typically be a small percentage of your trench excavation. If your shrinkage is high enough and your pipe/bedding volume small, you could wind up short of backfill material. Of course this all assumes your material is suitable for use as backfill. Where are you located?

 

[reddirtpusher]

There are digitizer based trenchwork programs that allow you to...
digitize the top of trench from profiles
digitize invert of pipe from profile
set a typical section for the trench including...
outside dia of pipe
the geometry of the trench including the depth of bedding
material, bottom of trench width, hieght of vertical rise from invert (if any), side slope on remainder of trench, additional depth of "select" backfill (if any) and shrinkage factor for the earth backfill.
The program calculates the length of the pipeline, the total excavation volume (inc the undercut for bedding,
the cy or tonnage of bedding, the cy or tonnage of select
backfill, the cy of earth backfill inc. shrinkage.
Some will also give you cut classification (how many feet at 0 to 6, 6 to 8, etc) strata volumes and cy of excess
excavated material.
Google "trenchwork"

My daughter wrote such a (dos based) program for me in the mid 80's.

Some vendors are Paydirt, Quest, and Insite (I think) and many more.

Good Luck