Dam building math

[Cam85]

hellow everybody it's been a while since I've been on here.

Anyway I need some healp with some mathematics can someone show me how to calculate the volume of a dam lets work on the assumption of 3 in 1 batters if I know the buy wash level the depth the top perimeter what is the equation of volume factoring in the batters and how to reverse that equation for the purpose of pegging one out.

Cheers cam.

 

[Cam85]

Also if the hole is going to hold the water and the wall is merely somewhere to put the dirt do I really need a proper core trench

 

[Shimmy1]

What's the size of the bottom?? BTW, nice seeing you back. Since the site has changed, it just isn't quite the same. Lot of familiar names just don't show up anymore.

 

[hvy 1ton]

If the pool level is below the bottom of the dam construction, I see no reason to core it. It should be fine with the topsoil stripped. As far as the math, too many variables. Need to define two dimensions to find the third. So if you know how long and how high, I can find how wide it needs to be. Use the area of a trapezoid where the top is 1/3 the width of the base and the length of the dam to define a trapezoidal prism. This might not make sense as i should probably be asleep, but i'll see what i can do tomorrow.

 

[Cam85]

Hey shimmy I don't know the cow cockies in Aus just want a dam i get given a volume and that's it go build I got nothin let's start at lets say 50 meter square at the top and 7 meters deep if I can get a volume on that and how to do it I may b abel to finger something out.
Cheers

 

[Cam85]

As 1 ton says the variables oh **** I'm in trouble test holes I pushed are good to 10 meters good creamy clay if we mark on the assumption that I can't go beyond 8 meter cut and I have a volume can we work backwards on a 3 in one all 4 sides to a square meter surface area I'm in a panick and got a metal block

 

[Cam85]

Hang on 1 ton is on to something can we do the math a Egyptian pyramid and turn it upside down hells bells my poor brain is fried

 

[Cam85]

I have to quote on this so I have to factor in strip push stack batter off the hole level off wall batter off wall push top soil back on trim up

 

[Shimmy1]

Hell, I thought you were going to give us something hard. Here's how I do it. The slopes are basically triangles, and 2 right triangles make a square. So, if you take the length of 2 of the sides, and figure it like a square, that will be all 4 slopes. Then, the center is easy, just whatever is left. I'll just keep it in meters-square. 50+50 (2 sides) is 100. 3:1 slopes, 7 (deep) × 3 is 21. So, 100×21×7 equals 14,700 m³ for the "batters", and 9×9×7 is 567 m³, for a grand total of 15,267 m³. I don't know how deep your topsoil is, so you're on your own there, but it's just 50×50 times whatever the depth, say quarter of a meter, so 50×50×.25 equals 625 m³ of topsoil.

 

[Crook_Donk]

I was thinking of the excavation volume as an upside down pyramid with the top cut off.
If that's the case, then work out the volume of the pyramid with the top still on, and take away the volume of the top that isn't excavated (which is itself a pyramid). That is two pyramids volumes to work out.
For a 50m square with 3:1 batter and 7 metre depth, the bottom of the dam (base of unwxcavated pyramid) would be 8x8 square (7x3x2 =42, leaving 8m additional). Keeping the 3:1 ratio, the height of the top of the upside down pyramid that isn't excavated is one third of half the width (8/2 =4.0m, divide by 3=1.3m). The volume of the unexcavated pyramid is then 8x8x1.3/3 (vol of pyramid is one third height x width x length) = 28m3. Take this volume away from the excavated pyramid assuming you excavate the entire volume right to the tip (50 x 50 x 8.3 / 3) = 6920m3 gives a total excavated vol of 6892m3.
Hope this is not confusing. I'm better with pictures than words!
Cheers

 

[Queenslander]

Go to your nearest Elders branch and ask for one of their notebooks.
All sorts of helpful info for cockies.

 

[Dickjr.]

I still use graph paper , but I have a calculator by calculated industries that can do cubic meters/feet. It works pretty well and was only about 30$. If its a bid job I will add 10% to C M A.

 

[Scrub Puller]

xxxx

 

[Scrub Puller]

Yair . . .
Guday mate, it's good to see you back!

The fellers have covered it pretty well I reckon. I never went to school much and always had trouble working stuff out.

I always imagine one batter turned upside down on top of the other gives a hole with vertical sides . . . pretty easy then to work out the cubes.

As regards the core trench thing. I have built hundreds of dams and have never used a core trench . . . pretty hard to do with a dozer.

Far more cost effective on a farm dam to line with clay. Even here in the coastal sand country you can usually find enough clay on top of the granite to provide a lining of six inches or so.

Most times it works. An occasional leak under such circumstances is to be expected. . . . no guarantees implied or given.

Cheers.

 

[Shimmy1]

I was in a hurry this morning when I figured the cut, my numbers are off a bit. I did not account for the corners. I think crookdonk figured it pretty close. I guess early in the morning is not the time to write up bids, eh??

 

[DMiller]

We have Loess soil here, APPEARS to respond as a clay but not even close. Is as granular but like salt square edged granules not round like regular clays. Water soaks into it fairly easily so they prefer to line our ponds with clay from north of the MO river as this stuff when saturated will slough. Dry it will hold a wall cut square for-seeming-ever, wet it flows like sand.

 

[D6c10K]

On farm ponds in our area it's required that a key trench be cut below the dam and lined with clay to prevent leakage. (If you're getting cost share from the gov't)
Most often ponds here are built across and existing ditch between rolling hills, so much of the dirt in the center of the pond is already gone....so much so that it can be difficult to find enough clay to build the dam.
That's one of things I need some experience with before tackling a pond . I'm sure guys that have been doing it for years can look at a site and know about how much dirt they've got to work with.
Short of doing a topo of the site and and engineer to calculate it, I couldn't judge withing a mile of the cu. yd.

 

[Scrub Puller]

xxxx

 

[oldrusty]

Hight x width x lenght divide by 27 will give you cubic yards. take each foot of your pond in depth and use the math for each layer then add the layers for total. don't forget that as you get to the top each layer will be larger because of the slope. if you want you can figure the core from the bottom to the top as one block and then treat the sloped part as a triangle. figure the triangle as a rectangular section and divide in half for the actual yardage. it will be close enough for estimation. remember that the yards in the cut will be bank yards and sfter you dig it out it will occupy maybe 10% more volume

 

[DMiller]

Comes a bit easier if you simplify the math, halfway up the slope from bottom figure perimeter lengths, if you calculate as a rectangle LxWxH at that point will give a very close value of volume. Basically folding the triangle of the lower slope onto the angle of the upper slope.