Trafficable surfaces above 60 mil HDPE Liner System??

[claytill]

I am currently designing a sludge pond that will require cleanout ~every 2 to 3 years. A trafficable surface is required to support cleanout equipment and our design consists of roller compacted concrete (150 mm), underlain by 3/4" crushed road gravel (200 mm thick),which is underlain by a 32 oz non-woven geotextile (liner protection) follwed by a double 60 mil HDPE liner.

My concern/uncertainty is that during the construction phase the 200 mm of gravel a) may compromise the primary liner during placement of the roller compacted concrete (ie, loaded trucks with RCC), b), 200 mm of gravel maybe insufficient thickness and should be increased, and/or c) maybe a sand layer is required to provide additional liner protection? If anyone has experience with such applications, I would appreciate your comments. Also, any references you could point me to would be great.

 

[Ron]

claytill....60-mil HDPE can have puncturing problems with a gravel bed above it, depending on the type of gravel. If it is crusher run, that's a big problem as would most cleaved aggregates. Washed river gravel is the least likely to cause an issue.

Still you are putting heavy loads on top of the gravel as you place the RCC. Depending on construction activity, you can tear the liner or puncture it.

Have you considered shotcrete instead of gravel and RCC? Shotcrete on top of a thin gravel topping would be ideal.

 

[Prepakt1]

You could also cover with some concrete fabriform matting.
Being a fabric that is pumped full of concrete this will keep anyone from having to work on top of the liner to pour concrete,The fabriform being nylon will not damage your liner and will provide a surface that you can use for running equipment on.The main downside is that it will not be perfectly flat and not advisable to scrape with a loader

Intrusion Prepakt

http://www.marineconcrete.com

 

[TDAA]

I would not be too concerned with puncture on 32oz of fabric; however, tearing / distressing is very likely over that little cover.

We have typically held to 3 feet of material under non low ground pressure equipment, and then held the LGP equipment to a min of 12 inches (18 preferred). You could likely go with a thick gravel road (or thinner if placed with LGP) and cover with shotcrete to forma a durable surface.

Look at the stress distribution of the planned equipment, and see what forces / pressures are anticipated. That can help determine minimum cover. I would definitely be careful with the compactor for the RCC, if you go that route.