Erosion in Median
Erosion in Median
(OP)
We are building a 40 mile long guard cable project. I'm concerned about the possible erosion around the post during the period before grass has been established. The Soil is a silty clay with a liquid limit around 50. Standard ditch checks will be used. I had a previous project that required the use of blankets to prevent the erosion of loess soil which is highly erodible. We do not anticipate that this soil will erode as readily but any erosion that does happen will be difficult to repair with the post installed. Give me a hand here I want you thoughts. I plan on doing some calculations but normal procedures do not really apply. I'm assuming that the ditch checks work as detention storage but I don't have time to make this a research project and there are a host of things to consider. The actual physical properties of the soil are not even readily available from the standard soil data such as liquid limit and plastic limit.





RE: Erosion in Median
Soils that are easily eroded sometimes include dispersive soils, particularly if the soil is a moderately plastic clay. You can run a quick check on the soils to see if they may be dispersive. Get the soil samples already taken - run crumb tests on them. The crumb test checks for dispersive behavior. If you get even 20 percent positive, then you should expect problems. The test isn't perfect, but if it says you have a problem - you have a problem. No false positives -
Read this document to get a handle on testing dispersive soils - includes the crumb test:
www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-1906/a-XIII.pdf
Standard lab tests are of no use in identifying dispersive soils. Crumb tests are cheap - you need the soil samples, distilled water and smooth, clear plastic cocktail glasses.
RE: Erosion in Median
How long will it take to establish grass, and how many times do you expect to see rain with runoff and erosive velocities before then?
do a risk analysis
1) determine probability of failure ie: erosive flow occurs causing erosion damage
2) determine consequence of that erosion - what will it cost to repair?
risk = probability X consequence
compare that risk to the cost to provide the blankets or other erosion protection
RE: Erosion in Median
RE: Erosion in Median