Geofoam

[tolchijb]

Hi all. Does anyone have experience using Geofoam as fill below a hillside structure? Up hill there is an existing retaining wall holding back a street. On the down hill side there will be as much as 25' that needs fill. With a typical pier and concrete lagging wall with conventional fill on the down hill side, it becomes too expensive. Using Geofoam as fill will eliminate a $400,000 retaining wall and it will only cost about $150,000 for the geofoam. Through my research so far, it appears we can bench the Geofoam blocks into the bedrock and just shotcrete the face on the downhill side to protect the Geofoam. I do have a geotechnical engineer on this project and he is looking into Geofoam on his end. I would like to know what the communities thoughts are on this design idea, if there are pitfalls we should try to avoid, and any other useful insites you all see fit to respond with. Thanks in advance.

Josh

 

[BAretired]

I have no experience with this application, but it seems to be a very good idea. You would be replacing heavy soil with an extremely light material (about 1 lb per cubic foot for PlastiSpan void blocks.

I would think that good drainage is essential, but that should not be difficult to provide.

If you are going to have vegetation above the Geofoam, you will need to prevent roots from entering the foam material.

BA

 

[spats]

I used geofoam for a parking garage in Virginia back in 2000 (buried on one side), and hired a consultant who is expert in geofoam. His name is Dr. Dawit Negussey, and he is a professor in the Civil Engineering Dept. at Syracuse University. Don't know if he's still around, but he's the guy.

 

[BigH]

Recently geofoam is being used in highways in British Columbia, it was used for I-15 in Salt Lake City Utah - it has been used for railway bridge abutments. Horvath is another "expert" in geofoam (Manhattan University?).

 

[Prepakt1]

It is being used for highways embankments in British Columbia. I am curious as to the loading allowed and how much water it will absorb. I observed the foam being wrapped in polythene when being installed. If it absorbs water it could be very heavy indeed.

Intrusion Prepakt /marineconcrete.com

 

[BigH]

prepakt1 - even if it were 100% water, it wouldn't weigh more than the water (Yes, I know what I said!). A few years back I did a presentation to the Calcutta Geotechnical Study group on using lightweight fills for highway embankments and, as I remember, 1 m of soil is about 70 m of geofoam! They also have geocells which, in effect, is pvc pipes tied together side by side vertically and surrounded by geotextile - this allows water to freely flow up and down (fluctuate).

 

[kelowna]

I have used geofoam (actually in British Columbia).

To answer Tolchijb original question, it seems that geofoam would work nicely for that aplication.

To answer some of the other questions:

Geofoam will typically only absorve about 5% to 10% of its volume in water (or so I was told). The foam has to be completely confined to ensure it does not move and transfers loads properly. Uusually there is a plastic membrane around to protect it from soil and water. It also disolves in gasoline, so a membrane separating it from traffic seems like a good idea.

Load bearing is fine, and geofoam is manufactured in different densities, so you can choose depending on your loading. Typically there is about 1 meter of soil on top or even a concrete slab to distribute loads. Long term creep is a concern.

Installation is simple but very, very tricky. You have to ensure you start with a very level, flat area, otherwise stacking the blocks will not work.

 

[BigH]

and stack like bricks - with successive layer joints offset.

 

[tolchijb]

kelowna,

Is it "standard" practice to anchor the goefoam blocks in some way? It was brought up in a recent project meeting that a stiff breeze heading up the slope could conceivably lift these blocks causing a serious hazard to workers. Our thought was to drill rock nails through the blocks at some spacing to prevent any uplift or slippage of the stacked blocks.

Also, we do not plan to bear spead footings on the geofoam, but drill piers though the geofoam and socket into bedrock. I am thinking I will need to design the piers as unbraced through the geofoam since I cannot imagine it will provide much lateral support.

Thoughts?

 

[BAretired]

I agree that the geofoam should be anchored to the rock and that the piers should be considered laterally unsupported.

I'm not sure how easy it will be to support a drill rig on the foam. That sounds a bit bouncy to me.

BA

 

[kelowna]

In the roadway applications I have used them(and I am using them again in a new job), the geofoam is completely encapsulated (top and all sides) by a soil layer of at least 1 meter thickness. That prevents them from shifting. Hence, no ancoring has been required and they do not move. Anchoring them is a problem because they are not that sturdy. I guess you could anchor a wire or plastic mesh which then you wrap around them.

It is true that during installation, wind will move them around (we had a block going away like the house on the Wizard of Oz movie). Not a problem once covered.

The blocks do not provide any significant lateral support. Calculating the piers as unbraced is the best.

Drilling through would not be a problem as long as you have the blocks properly covered. In a roadway application you have highway traffic on top, although we have the road asphalt layers and 1 meter of soil. Drilling could be a problem because of the actual expanded polyestirene pieces blowing away. I would suggest pre-form the piers as you place the geofoam.