earthwork quantity using computer simulation 1

Does modeling earthwork quantities using computer software make the quantity accurate? Of course a thorough knowledge of earthwork and related is a must, such as the different methods of quantifying earthwork and shinkage factors due to compaction, and more, and more.

As a cad technician, I have recently experienced several projects where I have had to model the earthwork and rock quantities on a site. But I am not sure how accurate my quantities are.

I use the geotech's report for shrinkage factors for reuse of native material compaction (gives a percentile per cubic yard), and I believe the composite volume check is the most accurate, am I wrong?

Also...what else should I take into consideration?

Thanks for your help.

 

[jheidt2543]

Here are a few thoughts to consider:

1. Nothing about computers makes anything more accurate. It all depends on the input and the interpretation. Higher precision does not necessarily mean higher accuracy.

2. The input depends on how the original information is aquired, on the ground survey, GPS survey, photogrametry, etc.

3. Most all computer quanity systems for earthwork come up with similar quantities. The ease of input/output make the main difference. However, there are some special situations that some programs handle better than others, for example the inside and outside curve exavation wedge along a road bed is sometimes missed in some programs.

4. A lot depends also on what program you get use to and how much checking of the quantities generated you do. Just because the computer says x= y cubic yards does not make it so.

5. The best thing about the comupter is the ability to do "what if" revisions. You can do the same takeoff 2-3 times in half the time it use to take by hand to do it once.

Some food for thought.

 

[carlorom]

As a surveyor I wholeheartedly agree - It depends largely on the input survey method etc.Also the precision to which the computer rounds of data is critical.

In general you could have a rounding off to say 0.01m over one hectare that could make a considerable difference to your quantities - some computers round up others down or it depends on the settings - the frequency of surveyed spotshots and the resulting modelling (triangulation) of the surface.

We have had to resolve disputes between earthworks contractors (counting the number of lorry loads) versus quatities established from before and after surveys. The difficulty was usually the density of spotshots as well as the compaction factor you mentioned.

 

Thank you for your replies.

I have also ran into the same problems with contractors when comparing the before and after surveys, cross sections, and trench shots to see how much the contractor will get paid for rock removal. This problem is much more simplified by computer.

I did not want the contractor or the client to get ripped off. Thanks for your input.