Stockpiles Measured Dry then after 90 mm of rain

Hi ,

Recently measured a clayey gravel stockpile dry then after 90mm of rain and the volume had apparently increased by 300 m3 after the rain.

Total volume was 2750 m3 in the dry then 3020 after 90mm rain.

Footprint areas(2060m2) remained the same.Standing water in troughs of stockpile would probably be seen as solid by pix4d.

I flew the stockpile at 50 m without GCPs.


Thanks! This is a perfect example of why it is so important to understand the materials that are being estimated if you are delivering quantities to a client. If you are not familiar it is in your best interest to encourage and train them how to do it. Knowing densities and shrink/swell factor will make a big difference if you’re trying to get to the 1%.

I am familiar with bulking factors of mined materials but have been unable to find any tables on swelling /shrinking factors of materials sitting on a stockpile subjected to heavy rain followed by intense sun(I am in Angola)

Obviously with that much rain you are going to have allot of erosion so there’s no telling how much was lost that is not even a part of the swell/shrink discussion. Swell and shrink factors are tough to state factually across the board because they vary greatly across regions so it’s probably not a good effort unless you are talking to someone in the same area as you. Also, there are three kinds of shrink and swell that can come up. Factors attributed to water, from excavation and embankment and from air pockets. Here are a few averages most common in our region with the water factor. (Swell/Shrink)

Loam-based: 25/15
Clay-based (Hi PI): 40/35
Clay-based (Hi PI): 35/30
Sand-based: 10/5
Gravel: 5/0
Sedimentary Rock to Crushing: < 6" 10%, 6-12" 20%, 12-24" 25%, > 24" 30%
Igneous Rock to Crushing: < 6" 15%, 6-12" 25%, 12-24" 30%, > 24" 35%