Need help with cut/fill calculations
Need help with cut/fill calculations
(OP)
Hello:
Can anyone point me to information on the web about how to do cut and fill calculations for grading?
Say I have a 500' by 700' area. I take shots every 25' to form the grid. I would like to know the total cut/fill for the site (not worried about compaction -- yet)
I've checked mainly university engineering sites for info and found a little, but not enough information to calculate what I need.
Thanks,
Richard
Can anyone point me to information on the web about how to do cut and fill calculations for grading?
Say I have a 500' by 700' area. I take shots every 25' to form the grid. I would like to know the total cut/fill for the site (not worried about compaction -- yet)
I've checked mainly university engineering sites for info and found a little, but not enough information to calculate what I need.
Thanks,
Richard





RE: Need help with cut/fill calculations
RE: Need help with cut/fill calculations
It is probably amazing how many of the younger members have never worked with plans and sections that they have drawn up given computerization these days.
RE: Need help with cut/fill calculations
Also, I currently AVERAGE the elevations to get the proposed new elevation (for road beds, chicken house pads, homes, etc). Is there a better way?
Thanks again,
Richard
RE: Need help with cut/fill calculations
1. If you are going to do this kind of work you should really get a copy of "The Building Estimator's Reference Book" by Frank R. Walker Co. It covers all aspects of estimating, but in particular has a detailed outline of earthwork calculations via the Cross Section Method and the End Area Method. There are a lot of other good books out there, but this one covers all aspects of estimating at a resonable price.
2. When doing earthwork cut & fills, you should keep the various operations separate; Clear & Grub (SY), Strip Topsoil (CY), Cut to Subgrade (CY), Fill to Subgrade (CY), Marsh Excavation (CY), Clay Excavation (CY), Unclassified Excavation (CY), Rock Excavation (CY). Then the fill going back in should be separate too in (CY); Granular, Clay, Unclassified, Topsoil, Stone Base etc. All these items are priced separately and it is easier to take them off at the begining. You also have to consider haul-in and haul-out quantities.
3. One of the biggest arguments in earthwork is how many times each yard of dirt gets moved, it is not just the net cut/fill quanitity. If you keep each operation separate, then it is a lot easier to keep track of the movements and costing.
There is nothing wrong with doing these calculations by hand. It is a lot easier by computer, but you learn to understand it a LOT better if you do a few small projects this way, then go to the computer.
Best of luck.
RE: Need help with cut/fill calculations
RE: Need help with cut/fill calculations
smurrison@cox.net
Scott Murrison
RE: Need help with cut/fill calculations
RE: Need help with cut/fill calculations
Average end area calculations between sections is the best method for hand calculations. The number of sections depends on the topography. Compaction must be considered for the final design.
In short, average end area(s) is the best method for use by hand calcs.
I am in Houston Texas, we have flat topography, and at times move 100,000 to 1,000,000 yards of the Earth.
RE: Need help with cut/fill calculations
When I level a pad, for example, I first clear the trees with the Cat. Then, I take shots at 25' intervals for the whole pad area. I then put these on the corners of a grid and average all the shots to get the "proposed" elevation. Then I figure the cut/fill for each grid section by adding all the cut and all the fill for that section and multiplying those by the corresponding grid area (25x25=625). If 3 of the corner points are cut, then I average those and multiply that by (3/4 x 625 = 468.75) to get the overall fut for that grid. Then, do the same for fill. Then I add all the cut and all the fill to get the totals. Then I divide total cut by total fill to get a percentage. Hopefully, that percentage is about 1.2%.
I know this is NOT the full technical method. It does not consider slope, compaction, etc. But, will it suffice for my simple operation?
Thanks again,
Richard Hollingsworth
RE: Need help with cut/fill calculations
That is the cross-section method in a nut shell, but I don't know why you really need the % cut to fill. If you are allowed to use the cut material for fill, all you really care about is how many yards of fill you need (using a suitable compaction factor) and how many yards of borrow or haul-in.
Using a 25' grid should provide pretty accurate quantities. Most of the small construction sites I did cut/fill calcs for I used 50' or 100' grids depending on overall elevation changes across the site. And, of course, you can use different grid sizes for different areas of the site too.
RE: Need help with cut/fill calculations
1.) It is easily explained to contractors and clients.
2.) It is commonly used throughout the construction industry and can be defended in a dispute. Try explaining some engineering software to a judge or jury.
You might want to plot your end areas to scale on graph paper-this will allow a better visualization of cut/fill.
Counting squares of the grid would give you check in your calcs. To bring this idea into the 21st century you could create a grid in Autocad and use Autocad to calc areas. I believe that you would need extra stations at the transition point between cut/fill. You will need to know the expansion factor of the material you are excavating etc.
We used this method for 40 miles of railway grade in the early '70s and only had real problems with placed material.
RE: Need help with cut/fill calculations
I agree that the Average End Area Method (AEAM) is also a good method for earthwork calculations, particularly if you plot out the sections. An earthwork company I know of wrote their own program 25 years ago and used the AEAM method and the program plotted each section as a viusal check. However, my sense of it is that, most earthwork for building construction is done by the Cross Section Method (CSM)and most highway/railway dirt is calculated by AEAM.
I learnd both methods at the beginning of my career and have used both, but CSM seemed to fit the projects I worked on the best. But, the best method is the method you understand and feel most confident in. As I said earlier, doing the take-off by hand teaches you a lot and when you "graduate" to the computer you have an understanding of what the computer is doing. When we finally computerized, there wasn't a happier guy. I use to hate sitting up until 2:00 AM doing take-off extensions!
RE: Need help with cut/fill calculations
Good Luck
RE: Need help with cut/fill calculations