Lightweight polystyrene fill for flexible pavement subgrade

[Okiryu]

Have you ever used lightweight EPS fill as flexible/rigid pavement subgrade? If yes, what CBR/k can be used? Perhaps, the EPS compressive strength can be correlated with CBR/k? Traffic is composed of medium size forklifts (10-15 kip axle forklift, max 50 operations/day in 25 yrs design life). This is for an industrial warehouse slab-on-grade. Based on these conditions, is it a good idea to use EPS for flexible/rigid pavement subgrade? In my opinion concrete pavement is preferable but client is approaching for flexible pavement because the site is on a reclaimed area which has potential for differential settlements. However, some studies indicate that remaining long-term consolidation settlement due to fill placement during the reclaim project may be about 30 mm which I feel are acceptable. I am planning to measure pore water pressures to check if they have been dissipated. Grade will not change so additional loading which may result in additional settlements is not expected.

 

[oldestguy]

I'd prefer concrete pavement heavily reinforced. If necessary in years to come do slab jacking to raise low areas.

 

[Ron]

Okiryu...I have not used EPS; however, I have used cellular concrete as fill over areas with poor soil conditions to keep the overburden loading down and to provide strength as well. This was on a paper mill project over swampy areas in the southeaster US. The cellular concrete had a low unit weight of about 30 pcf as compared to the removed soil which had a unit weight of about 100 pcf.

Traffic is heavily loaded trucks and I designed a flexible pavement above the cellular concrete fill.

 

[SlideRuleEra]

...the site is on a reclaimed area which has potential for differential settlements.

Maybe a suitable geotextile fabric will be of value. I've never used EPS, but have had good results with the fabric and compacted suitable (soil) backfill.

http://www.SlideRuleEra.net

 

[Okiryu]

Thanks OG, Ron and SRE... I like your suggestions. We need to check if performance of the slab will be controlled by the settlement of deep alluvial deposits due to fill placement during the reclaim project (I was also thinking on secondary consolidation settlement affecting this site) or if it will be controlled by the subgrade support. We are still on conversations with the client so I will post again once I have some more solid idea about the project requirements...Thanks again !

 

[EireChch]

SRE a fabric will do little to reduce differential settlement. A triaxial geogrid would be perfect.

Okiryu - I would contact tensar. They can offer you the best advice as to what geogrids could be used. They will also do a preliminary or detailed design.

 

[Okiryu]

Thanks EireChch...unfortunately Tensar does not have offices in Japan but I will check with our local geosynthetics manufacturers.

 

[BigH]

Styrofoam has been used in many places as lightweight fill. In Norway it has been used under rail bridge abutments. Several US highways (I-5, I believe is one off the top of my head) where styrofoam was used. There area a few issues - namely potential for fire - but the sides and the top will need to be fill protected. Horvath has written extensively on its use.

 

[Okiryu]

Thanks BigH. Looks like based on the historical good performance of EPS for supporting pavements, the EPS should not create problems if it is used as subgrade material.

 

[SlideRuleEra]

ErieChch - Thanks, lesson learned. I should have explained our application of filter fabric, and I suppose it does not apply to Okiryu's situation.

This was for unpaved roads for off-road haul trucks. Placed 2+ feet of compacted (in layers, during placement) crushed limestone base on top of the filter fabric in swampy areas with year-round high water table (similar to what Ron described). The filter fabric separates the poor soil from the crushed limestone to keep the base uncontaminated during compaction. The entire road settles (about 3" per year), but no issues with differential settlement. Once a year, or so, 3"+ of base is placed on top of existing.

http://www.SlideRuleEra.net

 

[fattdad]

We have a section of Interstate I81 where we used EPS for a bridge approach. The project was a lane widening effort. We had to rebuild the bridge to accommodate the extra lane. We had to do a side-slope fill for the new bridge-lane approach. We were mindful of the limestone and the changing loads - their effect on the rock stability. So, we did a net-neutral fill (nearly) using EPS.

I'm certain that we had an approach slab of reinforced concrete. I'm also certain that there's flexible pavement on the top. We wrapped the EPS in membrane, owing to concerns about fuel spills.

Now I need to figure out the basis for the pavement design. We may have had some granular fill atop the EPS?

f-d

ípapß gordo ainÆt no madre flaca!

 

[EireChch]

SRE - yes a different application. The fabric stops the aggregate from "punching" into the soft layers underneath. Always a good idea to separate different soil types.

f-d we have done a little bit of work in EPS and would always spec a 1m layer of aggregate on top. Now it was for residential applications not to the same scale as what you would be doing.

Our reasoning being that EPS is better at taking spread loading. Point loads are not good. A 1m layer of aggregate would be a lot stiffer and would "absorb" some of the loading.

 

[geotechengineer1]

Not personally but I know in Alberta EPS fill has been used on a couple of highway projects in muskeg / soft soils, Highway 43 and another one I can't remember. I think they actually had the EPS buried under a meter or so of soil due to frost concerns though not directly as the subgrade. I was involved in a project where we use it as lightweight fill behind a retaining wall on top of a parakade where we had to limit the load.From my experience handling the geofoam blocks my feel is you'd get a pretty trash CBR out of it.

Some research that could be interesting:

https://ascelibrary.org/doi/10.1061/40866(198)21

https://ascelibrary.org/doi/10.1061/41165(397)465

There is also an NHRCP report that would be interesting and could contain the information you are looking for:

https://www.nap.edu/catalog/13759/g...r-geofoam-applications-in-highway-embankments