roadway over Landfill roadway over Landfill kechha2060 (Civil/Environmental) (OP) 6 Feb 12 12:26 Does anyone have any experience on designing/constructing roadway on top of landfill area. We are considering an asphalt pavement (8" thick 'no basis') knowing issue of maintenance. RE: roadway over Landfill beej67 (Civil/Environmental) 6 Feb 12 14:01 Is it for public traffic? Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com RE: roadway over Landfill MiketheEngineer (Structural) 6 Feb 12 16:07 My guess is a lot of pot holes and uneven surfaces.... RE: roadway over Landfill Ron (Structural) 6 Feb 12 20:50 I've analyzed/designed pavements for some strange applications ....what is your traffic and what kind of loads? RE: roadway over Landfill kechha2060 (Civil/Environmental) (OP) 7 Feb 12 11:02 Yes, roadway is for public predominately passenger car but truck loads are also anticipated. Design std calls for 20k vpd with 10% truck traffic. c RE: roadway over Landfill cvg (Civil/Environmental) 7 Feb 12 11:25 I would make sure your client realizes this roadway will require major maintenance on a frequent interval, regardless of how thick you make the structural section. Don't expect a 20-year design life. Expect significant and highly variable settlement. Also, collection and mitigation of LFG is a risk factor and additional cost you will need to address in your design and construction. another question - how long ago did they close the landfill, what was the closure system and what kind of landfill is it? RE: roadway over Landfill Ron (Structural) 7 Feb 12 11:34 I would create a mat of high modulus material (graded aggregate base, CLSM, cellular fill, etc), then design the pavement section on top of that. RE: roadway over Landfill MiketheEngineer (Structural) 7 Feb 12 16:40 Or build a bridge?? RE: roadway over Landfill Drumchaser (Civil/Environmental) 7 Feb 12 16:41 Bridge RE: roadway over Landfill fattdad (Geotechnical) 7 Feb 12 17:36 the problem with a bridge is the piles would penetrate the landfill, leachate and (likely) into the water table. I'd consider a soil raft (i.e., granular fill and geogrid) and anticipate a maintenance program.I'm pretty sure my DOT wouldn't accept this road into our system though. . .f-d ¡papá gordo ain't no madre flaca! RE: roadway over Landfill Dozerman56 (Civil/Environmental) 7 Feb 12 19:21 I don't know about over trash but I've seen a layer of geogrid and a foot or two of crusher run heal some really miserable earth. RE: roadway over Landfill cvg (Civil/Environmental) 8 Feb 12 09:11 except that a landfill is not earth, it's a pile of trash... the settlement will occur deeper in the landfill, not at the surface RE: roadway over Landfill kechha2060 (Civil/Environmental) (OP) 8 Feb 12 09:38 Landfill is solid waste and construction waste site. 3' clay cap, closed in 80's per records RE: roadway over Landfill civilman72 (Civil/Environmental) 8 Feb 12 09:40 If you have some time, you may consider an overburden load to promote settling, prior to actual road construction.You can also consider starting with a gravel driving surface for a few years and then adding asphalt when settlement and maintenance have (hopefully) started to decrease.But I agree with the previous posts, your maintenance costs for this type of road will be relatively significant. RE: roadway over Landfill cvg (Civil/Environmental) 8 Feb 12 10:25 how will you deal with LFG collecting under the pavement? RE: roadway over Landfill beej67 (Civil/Environmental) 8 Feb 12 16:29 If it was closed in the 80s, do you have some old surveys and new surveys you can compare, to see how active the settlement has been over time? I seem to recall anerobic bacteriological processes take some 30+ years to finish up in landfills, but that's from memory and it could be longer.If you want a highly creative solution, retrofit the landfill for aerobic bacteriological processes - basically pump air through it and also recirculate lechant to keep the temperature low enough to prevent it from catching on fire. That should kickstart whatever remaining activity it's got left, and the whole thing could be inert in a few months. Then build over the inert landfill.I was at Arcadis in the late 1990s when they did a pilot project that involved aerobic landfilling. I don't know if it ever caught on, but they were able to take a regular household trash landfill and turn the whole thing to dirt in a few months instead of what would normally have taken years. Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com RE: roadway over Landfill Drumchaser (Civil/Environmental) 10 Feb 12 21:45 Long Bridge. RE: roadway over Landfill chicopee (Mechanical) 15 Feb 12 21:34 beej67 is right about the settlement and its cause. RE: roadway over Landfill kechha2060 (Civil/Environmental) (OP) 15 Feb 12 21:55 thanx for your suggestion and insight. How expensive is aerobic process cost? bridge and surcharge are cost and schedule prohibitive RE: roadway over Landfill fattdad (Geotechnical) 15 Feb 12 22:37 o.k. I just can't find the citation, so I'm going from memory. . .Anders Bjarngard published his thesis and it had to do with the settlement of municipal waste landfills. Just like soil, there is initial "modulus-based" settlement (after all the trash does have some modulus value and there will be some immediate compression). There is also settlement as related to change in void ratio in the absence of change in effective stress - i.e., secondary compression. You see usually we are not dealing with consolidation as the landfill materials are usually not saturated and if so the permeability of the trash is pretty high.Anders Bjarngard looked at historical data from landfills all over the place and determined that secondary compression (C-alpha) is similar to that for soil - problem is that the value of C-alpha INCREASES over time to some value, "C-alpha-max." He provides graphed data and values for C-alpha and C-alpha-max. I used to (likely still do) have a copy of his thesis. If you google Anders Bjarngard you will find ASCE publications that you can purchase and I think these publications must cite his original work. They have interesting titles and may be great publications, but I'm not spending the money to further engage in this discussion. I am interested in what you find.I'm not taking anything away from what's already been posted. The variation in C-alpha is related to decomposition rate and all those anaerobic processes. I'm not sure that unleashing aerobic processes in a landfill is the right or wrong thing to do. If the debris has been in place for 30 years and you consider the extent of compression that's likely occurred, the forecasted settlement (compression) using secondary compression values may be manageable in conjunction with a soil raft.Face it, you are not doing "generally accepted" engineering practice and your client should recognize this risk before you sell yourself as some engineering expert.f-d ¡papá gordo ain't no madre flaca! RE: roadway over Landfill Caspercat1 (Civil/Environmental) 30 Apr 12 12:23 Would other factors be present such as possibility of flooding? Extreme temperature differentials? How soon must construction begin? RE: roadway over Landfill charnott (Civil/Environmental) 1 May 12 02:05 dont forget to locate the landfill high wall particularly if the landfill records are questionable for any reason. a series of geophysical survey transects perpendicular to the anticipated location of the high wall will do the trick and provided the correct methodology is selected will enable a profile of not only the high wall position but the inside slope and/or batters of the filled area. RE: roadway over Landfill beej67 (Civil/Environmental) 1 May 12 09:07 Aerobic bioreactor landfills are relatively new tech, and I'm not sure it's easy to retrofit an existing landfill with them - you may need to have planned it from the ground up. Wikipedia has a brief entry, and lists some examples. Maybe call one of them up.http://en.wikipedia.org/wiki/Bioreactor_landfill#Implementation_of_bioreactor_landfills Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com RE: roadway over Landfill hokie66 (Structural) 1 May 12 21:59 Geogrid, granular pavement, maybe a PSP surface? That way you could take it up and relevel periodically. RE: roadway over Landfill Riversidean (Civil/Environmental) 15 May 12 16:42 Why are you building an Asphalt Road on top of a landfill? Is it to dump trash? Are you worried about weather causing mud and possible sticking issues? Working at a public landfill department Asphalt Concrete does alright unless major settlement occurs. Especially since Asphalt Concrete is flexible to a degree anyways. At the department I work at we typically only use asphalt concrete for customer roads steeper than 9%. Anything less we typically use will a purely aggregate base road leading up to our wet weather pad. If the weather is nice and the soil is not muddy we send our traffic to our active dumping pad which only has dirt roads. If you do this make sure you have a rumble rack at the exit to the landfill so as to clean the customer tires before they exit the landfill less you want public roads getting track out on them. RE: roadway over Landfill oldestguy (Geotechnical) 25 May 12 16:10 I see your question relates to those with experience on this subject. From what I can glean from those above, it would appear that Ron is the most experienced. I'd go with his advice. I have seen many a landfill operation, but have not designed the pavements for the access roads. In most cases they were done by the usual local municipal standards and served well. Any major settlements easily corrected.