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200 YARDS OF BOG ROAD

200 YARDS OF BOG ROAD

200 YARDS OF BOG ROAD

(OP)
I'll probably end up paying to improve a gravel road which passes over parts of a bog in Northern Wisconsin. The road has been there for over 60 years and two spots sink into water table. Roadway is 15 feet wide. Low spots have been filled with stone several times. The stone sinks in about 5 years.
 Is Geotextile fabric an option here? Is there a way to use it over the sink holes? Holes sink to 14 inches below water table.
Town refuses to pay for maintenance.
Phil

RE: 200 YARDS OF BOG ROAD

If the sinking area is 200 yards by 15 feet, then the geotextile won't do much good - that's too large of an area to bridge.  If the problem is spotty, though, a geotextile can help.

Is the road on private land, or is it a public right-of-way?  How much gravel would it take to raise the wearing surface above the water?



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RE: 200 YARDS OF BOG ROAD

This may not be an easy fix.  You should consider having a geotechnical engineer assess the problem. A few exploratory holes may be in order. Organic deposits, if that is the culprit, can compress as well as spread laterally under the influence of an applied embankment loading.  

RE: 200 YARDS OF BOG ROAD

(OP)
Focht3
 The low water spots are about 6 yards long. This is an easement road over government land. I'm currently negotiating a new easement and would like the Town to kick in some of the cost. The spots needs up to 24 inches of gravel and the entire 200 yards needs an added grade of 8 inches to keep it above water.

SirAl
 The actual open water of the lake varies from 100 to 500 yards to one side of this roadway. There are floating bogs at various points around this 270 acre lake. I know from the road foreman that some bog spots are as deep as 40 feet. What about wooden piles jetted into the low spots before applying the geotech material? If there's anything we got for building materials up here its tree trunks.

RE: 200 YARDS OF BOG ROAD

Looks like you are getting slow lateral displacement of the roadway into the lake. In such cases a berm would have been appropriate during the initial design. At this stage that would be some what expensive.

Some thoughts. If the fill sinks every five years consider using a light weight fill. With tree trunks you can construct a courduroy road (raft type construction) which was used initially to float roads on muskeg. This concept is still used on occasions and may be a cheaper alternate. Geotextile can be used over timber before placing the fill
This problem needs some innovation as costs can be high.

Several solutions are possible.

What type of vehicles in terms of weight and axles, traverse this roadway?

Are there any equalizer culverts in place?

You could also think of excavating some of the heavy fill and do a replacement with lighter weight material. This really depends on site assessment.

Thats all for now. Interesting problem that tests the geotech engineer in relation to cheap and workable solutions  

 

RE: 200 YARDS OF BOG ROAD

(OP)
Vad,
The roadway needs only to support passenger cars and an occassional electric company truck to repair downed power lines. The electric company trucks are no heavier than 6 ton ten wheelers.
"Equalizer culverts" sounds like a useable addition to reduce excessive softening of roadway by the periodic high lake level.
Would tree trunks be better used as corduroy floatation or as piles to reach stable soil at bottom of bog assuming stable soil was reachable?
Original road footprint came from 1890's narrow gauge railroad. I assume bog spots were originally filled by railroad Co. Logging was the original purpose.

RE: 200 YARDS OF BOG ROAD

You raised two issues with regard to the road, I will deal with the right of way firstly, and then some ideas regarding the road.

Who are the parties in the right of way (easement) agreement?  If the agreement covenants that a road be constructed, there is usually accompanying clauses specifying maintenance.  From your post, it appears that the agreement is between yourself(?) and the power company(?) and the State (government lands?).  What I am not clear on is the passenger traffic and how they relate to the easment agreement.  Is the passenger traffic something that has happened since the agreement date?

Where I am going with these questions is the fact that the agreement may make provision for maintenance or provide you with a termination clause somewhere.

As to the road, there are a number of cost effective solutions, however, burying the trees is not one I would recommend.  I've maintained and constructed county roads for over 15 years, and I have a few ideas.

You can call me @ (780)573-1884 if you want to go over some of the easement or road issues.

KRS Services
www.krs-services.com

RE: 200 YARDS OF BOG ROAD

PWS:

Thanks for the information. I am not in a position to offer any definitive solutions to this type of problem as my experience has taught me that everyone may be different. For piles, tops of piles will have to be tied together and across the road. I presume that you are thinking on having piles on both sides of the roadway. This venture would benefit from a couple of holes drilled in the roadway to depth. Culverts placed side by side can be used as well to reduce weight, if this is a reason.

Other thoughts are possible erosion if road is in a bend. I have seen logs tied in the lake to dissipate wave action especially in windy areas. Again site assessment would be important to determine whether erosion is a possible problem

It appears that KRSS has some ideas as well. Please let us know what solutions are offerred, so that we can be  enlightenment on what others have used and what works.

RE: 200 YARDS OF BOG ROAD

To your original question about geofabrics, they will not help support the weight of the road as there is nothing that they tie into.  As stated in most texts for geosynthetics design that if the subgrade will not support the embankment a geotextile will not prevent this.  Geotextiles will help only with lateral slumping of the embankment and will sometimes help cover sinkholes, must be carefully designed with very high strength polyester or nylon woven geotextiles.

RE: 200 YARDS OF BOG ROAD

I have had an engineer explain geotextile use in roads by saying it distributes a point load (tires) over a larger area of the subgrade (similar to a footing).  This is contrary to what I am hearing on this board which is you need something to tie into.

RE: 200 YARDS OF BOG ROAD

I do have some ideas, but firstly, I need to know what soils are under the roadway and whats avaiable for borrow.  Secondly, where are the road grade and ditch elevations in relation to the water table?  Thirdly, is this a lake or a marshland?  If there are power poles, do they lean?  If so, is the lean irregular between poles or symetrical through the area in question?

Most important, if you could address the issues I raised with the easement agreement itself, because it is still a little confusing.  From whaat heas been described so far, I would not be considering the use of a geocloth, but I'm not going to rule it out yet.

KRS Services
www.krs-services.com

RE: 200 YARDS OF BOG ROAD

johnhan76

Geotextiles are not stiff enough to distribute load the way you are suggesting.  Geotextiles have been used in roads before to prevent the movement of moisture and therefore help prevent the degredation of roads from freeze/thaw fluxes.  Other products such as glassgrid can help distribute load because they do not stretch as much and therefore mobilize their strength much sooner than a geosynthetic.

Geosynthetics have been used in bridging voids in Europe where they have problems with right-of-way but these are not ordinary road fabric geotextiles, they have strengths in the region of 50kN/m right up to 1000kN/m.

In order to carry load in anyway the material must either be anchored or stiff enough that it will not just bunch up and fall into the hole.  This can be accomplished by using a "tie back" length of up to 100m on either side of the void, depending on the diameter of the void.

RE: 200 YARDS OF BOG ROAD

I should also explain that the reason geotextiles are not normally used in roadway reinforcement, except for such locations such as logging roads, is that there is unacceptable deformation in the roadway before the geotextile is tensioned to the point where it will mobilize it's full strength.

RE: 200 YARDS OF BOG ROAD

(OP)
Krsservices and others,
Easement allows me "ingress and egress" to land locked property that has been in family for generations. This bog road and one other road, accesses the land locked property. The easement crosses government land over both roads. The government is directing me to use the bog road since they are closing the other access road. The current easement allows access over any government land adjacent to the land locked property.
 I'm beginning to understand the geofiber concept by the responses here. Most of the roadway is high enough to be stabilized by more fill of the correct type and grading. It is the two low wet spots that continue to sink and fill with water. The two low wet spots are about 6 yards long. If the geofiber was anchored in dry fill by wrapping around tree trunks layed across roadway and buried on both ends of the low spots would it hold?
 Would cabling trees together to form corduroy topped by geofiber and then gravel be useful?

RE: 200 YARDS OF BOG ROAD

You have not specified what sort of aggregate that you've been filling these two sinkholes with. I think I'd recomend excavation to a depth of 6-8 feet followed by refilling w/3-4 feet of 18-24" shot rock covered w/3 feet of 4-6" cobble, topped w/2-3 feet of 1 1/2" compacted crusher run. Inserting wood into an already saturated subgrade doesn't seem to make much sense and engineering fabric will never bridge such a large soft spot.
Rexcavator, E2H LLC

RE: 200 YARDS OF BOG ROAD

Just wondering if geofoam could be of use in this situation...

RE: 200 YARDS OF BOG ROAD

(OP)
swBausch,
 Thanks for the info on geofoam. Looks like the perfect solution for this location. Low tech, low price, ease of placement, I just wonder if it comes in different colors...
I'm sure the township hasn't tried this technique and just might be interested enough to kick-in some funds to try this out.
PWS

RE: 200 YARDS OF BOG ROAD

On the lower Kenai peninsula here in AK, we build corduroy roads with logs all the time thru muskeg.  This is done quite often, usually with success and to the chagrin of high tech engineers......sorry fellas.  A few years ago the borough upgraded the road that runs to my cabin, and instead of pulling up the coruroy that myself and my neighbors had laid down, they simply laid typar over it and then built the road from there.  Eventually a log corduroy will rot.  I have seen 30 year old corduroy roads that are still quite functional.  Mind you, we are driving loaded log trucks and other heavy equipment over them also.  If a log is completely submerged, it will last a long time.  (the Japanese buy timber from AK and submerge the logs when they arrive in Japan, keeping them this way until needed.  Sometimes the old technology is still the best!! 8^)

RE: 200 YARDS OF BOG ROAD

how about the use of a geogrid rather than a fabric geotextile? i have have some designs done by a company called Tensar, for CBR's of 1, and they have come up with two layers of geogrid (of different strength) in a layer of 600mm crushed rock, and this is for commercial access (articulated trucks)to sites over approx. 6m of peat.

RE: 200 YARDS OF BOG ROAD

bogtrotter

Using a geogrid is fine but you still need a separator to keep from losing your granular into the peat/bog or just falling into the sink hole, which I think is his more immediate problem.  If you plan on using a geogrid because of the idea that it is stronger, there are geotextiles available that are just as strong and would serve both as separator and reinforcement.  

I don't think that the geotextile option should be entirely ruled out but you need to have someone who has experience in the design of bridging voids, originally created for landfill cover design for when metal objects rust and create an empty pocket I believe, design this possibility.  You can contact any of the companies that deal in HS geotextiles such as Mirafi, Huesker or Synthetic Industries, I'm sure there are more but....

Good luck.

RE: 200 YARDS OF BOG ROAD

(OP)
I'm currently caught between Texas and Wisconsin and have been putting the problem to anyone who's interested. I've had discussions about combining GEOFOAM (and) GEOTEXTILES  (and) layering gravel. I won't have enough time before freeze-up to complete project. It'll have to wait until next spring I guess. Thanks for the ideas.

RE: 200 YARDS OF BOG ROAD

Rex was on the money.  I have had to rebuild sections of road using this philosphy.  If you have access to some cheap blast rock, say from a nearby mine or so, I would recommend excavation of the site below the natural gradeline (say four to three feet, depending on the type of soils and level of saturation, and place some medium to heavy geocloth in the trench and about three feet up each side of the excavation.  Next I would place the quarry rock (plenty of fractured face) or a 4" minus pitrun.  Static roll the fist lift of material, I'm assuming pit run, which should be about 8" or so.  If the grade is too spongy, place more pitrun and static roll when the grade is firmer.  If using blast rock, carefully place so as to avoid too many large a voids.

If using pit run, continue this fill to about 1 foot above the natural grade line.  If using blast rock, fill only to the top of the excavation, then use some 2" minus pitrun to build your grade.  

Construct the grade to approximately 2 feet above the natural grade line and finish by placing some road crush.

If you have filled to abour 6" above the natural grade line and the road has been sufficiently compacted, you may want to save some of the cost and construct using some good quality clay or other acceptable soils suitable for building H-20 or equivalent road grades.  I've had to repair some of the old corduroy roads and while they may have worked for the time they were first installed, the cost to rebuild the grade was not worth it.

Since you mentioned the road has been around for 60 years, I am assuming it was constructed as a means of getting around an old lake, and likely is insuffieciently draining as well, or the clays keep "pumping" water to the surface.
Next, construct the

KRS Services
www.krs-services.com

RE: 200 YARDS OF BOG ROAD

PWS:

Many interesting answers/recommendations for your problem.
What are the risks. Try one. It can work or have the road settle after another five years. Sir Al has the correct approach, one that I personally like i.e try to find the reason for the problem and then decide on the solution. Now failure may still occur despite the best efforts. If it does then you are at least knowledgeable on the error and you are better able to move to another solution which you may have thought about, but chose the other one instead.

There are a lot of fixes which are often used by many of us and reasons for their good performance are not entirely known. Some call it experience. This is the beauty about the subject. However, when there is risk we often have to know the premise of why we apply a solution as we may have to defend ourselves at a later stage. Irrespective of the risk my personal approach is to wrestle with the problem and satisfy myself before applying a solution. If it fails then I am enriched by the reason and likewise if it succeeds I am able to discuss why, when providing a recommendation for its future use.

The missing links-site characteristics, understanding etc are in your domain and only you can decide at this time.

Good Luck

RE: 200 YARDS OF BOG ROAD

(OP)
KRSSERVICES and REX,
  My first thoughts were to excavate and to refill with large quarry stone with layers of smaller road grade fill in about three or four layers on top of that. However the bog material I think is at least 20 feet deep in these holes and sits on top of glacial sands and till. I think... it will be less costly to attempt to float the roadbed on the bog material with some of the above mentioned techniques. The coming winter will give me time to reflect and analyze my options.
 As VAD so wisely put it, "wrestle with the problem and satisfy myself before applying a solution".

Happy Holidays!
 

RE: 200 YARDS OF BOG ROAD

PWS,

Geofoam is currently a high-profile material as you can see from the various search-engine hits.  Since many of the projects are public, there may be a public-affairs/liason officer who knows of the success or failure of the implementation.

There may be a project near you that would allow a site inspection?

RE: 200 YARDS OF BOG ROAD

Maybe I'm missing the point but the road only sinks at two locations for about 6m each - that's 12m by 4.5m or some 55 sq m.  If if only sinks 1/2m, say in 5years, that is only a couple of truck-loads of gravel.  I'd say it would be cheaper just to maintain the two sections. To dig out extensively to get down to "near" bottom would like incur a much greater cost than the couple of trucks every five years.  You could dig out a few metres, replace it with encapsulated hog-fuel (tree barks - or saw dust) and then get at least 1m of good sand and gravel above it.  This might reduce the pressures enough to make the maintenance once every 10 years.  

I had a project somewhat like this in the Burnaby peat plain in British Columbia back in '84.  25 ft of peat over 25 ft of soft clay.  The truck maintenance facility was on piles and 3 ft above the original ground level.  Needless to say, they had to redo the sloping entrance every few years as the trucks couldn't take the sharp curve at the top. I dug out 6 ft or so and replaced it with Elastizel - foamed concrete - and it worked like a charm.  But then, this is much more expensive - but you might want to consider it over geofoam since it has about 100psi compressive strength - better than most very stiff clays!!

RE: 200 YARDS OF BOG ROAD

(OP)
No BigH, I think you restated the problem accurately and I think your solution parallels my own compilation of ideas and solutions from the other engineers who have weighed in on this forum. If I can't convince the local government unit to maintain this section of road then I'll seek to use the least expensive most practical solution and do the maintenance myself.
PWS

RE: 200 YARDS OF BOG ROAD

I worked on a county road project with very similar issues, albeit the entire roadway was settling, not just pockets of sinking material.

The County wanted to widen a road that was originally built on 40+/- feet of peat, through a lake.  The solution to the roadway settlement for that project was two-pronged:

1.  Preload areas prone to settlement to compact underlying peat soils.  Time for preload varies depending on depth, underlying materials, etc.

2.  Construct roadway using lightweight fill to minimize longterm settlements.  Hogfuel (large conifer wood chips) was used.  

3.  Use geotextiles to hold lightweight fill lifts together.  Geotextile was installed, then a lift of hogfuel, then another geotextile, etc.  Used 12-18" lifts.  Wraps were tied back about 6-10 feet (can't remember....) from the embankment face for the 80 ft wide road section.  The geotextile wrapped around the embankment face at each lift.  I believe this approach is called a Hilfiker wall, or something like that.

For your situation I would consider the following approach as a long-term solution:

0.  Install silt fences or equal to prevent muddying up the lake.
1.  Place all your surfacing materials over the first soft spot as preload.  Configure in a way that is acceptable for temporary access, e.g. a "mound" shaped to be driven over.  Allow the material to settle a while (ie months).
2.  Move surfacing materials (preload) to next soft spot, retaining enough for step 4 below.
3.  Excavate the roadway in the soft spot vicinity say 5 feet deep and install say two lifts, 12-18" thick, of hog fuel/wood chips with geotextile fabric separating layers from each other and native material.  Place and compact hog fuel in 6 inch lifts for greater stability.  Extend geotextile past the soft spot to tie into more stable material.  Cover any exposed geotextile at embankment face with hand-placed riprap to protect from UV.
4.  Install 12 inch +/- surfacing layer on top of upper lift to final grade.  Could use 6 inch compacted native topped with 6 inch crushed.
5.  repeat at other spot.

Good luck

RE: 200 YARDS OF BOG ROAD

bltseattle - nice case history!

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