thiswilldude – posted 31 August 2002 14:22
I have stretched string accross the yard, between to level heights in order to gauge the depth of a dip in the yard. As it turns out it is quite a significant difference over quite a large area. How can I figure out how much compacted dirt to get? Is there some type of formula so that I do not buy too much or too little?
seed – posted 31 August 2002 16:36
thiswilldude, measure the length and the width of the depression in feet, and the deepest depth in inches. Now multiply these three numbers, and divide by 800. The answer tells you the approximate number of cubic yards to fill a circular (or elliptical) depression, with a spherical (or spheroidal) bottom.
For example, if your stringline is 40 feet long when it spans the depression, and it is also 40 feet wide in the cross direction (circular), and the depth is 6 inches, then you will need:
40 X 40 X 6 /800 = 12 cubic yards
If the depression is elliptical, e.g., 40 feet long, 20 feet wide, and 4 inches deep:
40 X 20 X 4/800 = 4 cubic yards
The shape of the depression makes little difference, as long as it all goes down to one center. For example, a circular depression 40 feet across with a conical shape and a flat bottom 20 feet across will need 13.6 cubic yards, compared with 12 cubic yards above. In the extreme, a depression, with a perfectly flat bottom and perfectly vertical sides will need 23.27 cubic yards.
These calculations can be verified by the formulae for partially filled spheres and cones: http://grapevine.abe.msstate.edu/~fto/tools/vol/
Getting further from pure geometry, depressions can undulate, with some ups and downs, which will require less backfill. In those cases it would be better to isolate the individual deepest depressions for measurements, and add up the results for the separate depressions.
Just curious – wouldn’t it be easier to move the dirt from the high points to the low points?
Phil
thiswilldude – posted 01 September 2002 06:31
Thank you for the help!
The thing is; the high points are the original height of the yard and follow the irrigation intentions. When the town decided to do some road work, they dug up some of the yard and when they allegidly repaired it, they left a sort of rough terrain ditch in the middle of the yard. I think they took dirt with them. The ditch they they have made is more like a rectangular lake when it rains. That is, it tapers, it is not just an immediate drop off. The water valve used to be flush with the lawn now it sits about eighteen inches above it.
buy using the high points I would have high side walks.