How Much Void in RipRap
How Much Void in RipRap
(OP)
I am trying to estimate how many tons of riprap per neat cubic yard of placement. I am thinking along these lines:
1) Determine riprap density from source...assume 155 lbs/ft3 in this case. That's about 2.09 tons/cy of 'rock'
2) Now the part I need someones experience on is how much void to factor in. If voids account for 33% of the total volume then this reduces to 1.5 tons per 'neat' cy. I realize this can vary, but what we have to use something. I think the void ratio would also vary by what size of riprap is being placed. What void ratio would you use for the
a) 1/4 ton riprap
b) 1 ton riprap
c) 3 ton riprap
d) 6 ton riprap
3) I would also use this information to determine the quantity of concrete used to fill the voids if placing concreted riprap.
Thanks for your help
1) Determine riprap density from source...assume 155 lbs/ft3 in this case. That's about 2.09 tons/cy of 'rock'
2) Now the part I need someones experience on is how much void to factor in. If voids account for 33% of the total volume then this reduces to 1.5 tons per 'neat' cy. I realize this can vary, but what we have to use something. I think the void ratio would also vary by what size of riprap is being placed. What void ratio would you use for the
a) 1/4 ton riprap
b) 1 ton riprap
c) 3 ton riprap
d) 6 ton riprap
3) I would also use this information to determine the quantity of concrete used to fill the voids if placing concreted riprap.
Thanks for your help





RE: How Much Void in RipRap
RE: How Much Void in RipRap
Thanks for your interest. The specification on my job is a minimum 2.4 specific gravity. That's 150 pcf. The source I am looking at is 2.6, 162 pcf. That is the density of the "solid rock", higher than concrete. I assume (I hate using that word, but that is what brings me to write this question in the first place..) that there is 20-33% voids in the same volume that "stacked" riprap is placed. If there is 20% that amounts to 120 pcf for the minimum specified scenario. A 90 pcf volume amounts to 40% voids. That sounds reasonable to me too. Does anyone have actual field verified data on this topic?
Thanks!
RE: How Much Void in RipRap
Using a 1 cubic foot bucket as you would for concrete aggregate will likely not be adequate as your particle size is fairly large. Make sure that the box you build has dimensions of at least 3 times the maximum particle size on each side.
RE: How Much Void in RipRap
RE: How Much Void in RipRap
RE: How Much Void in RipRap
However with that said, perhaps this US Army Corps of Engineers document "Engineering and Design - Hydraulic Design of Flood Control Channels" may be of help. Here is a link
http:
be sure to check out "Chapter 3" and "Appendix H"
www.SlideRuleEra.net
RE: How Much Void in RipRap
RE: How Much Void in RipRap
Also, look at your spec because if you allow a certain percentage of smaller fragments, they will fill the gaps and could amount to a significant weight.
RE: How Much Void in RipRap
RE: How Much Void in RipRap