Excavating in Slime

Maybe a helicopter and clamshell?

One of these with a long suction hose.

thats a portaloo sucker , you're thinking of a vacuum excavation truck which could work if you combined it with a water canon mounted on an excavator dipper arm.

you wouldnt use your best vac truck on this job though ;)

I wouldn't use any vacuum truck, now that I understand the scope of the task.

Augers seems the only way to go here and the OP has arrived at an interim solution, I think, with the reinforced roadway.

What sort of materials are there you can use? Any wood available to make a floating platform? Or water to turn the wet clay into a slurry you can pump out?

You might consider buying some floating roadbed made for use in swampy areas:

http://www.sportslawn.com/portatrack/portatrack.htm

We tried trees, we have trees aplenty. We built a platform for the 490 and it sank into the muck. We managed to get the 490 out before it was lost, but the platform settled about 10 feet down with geysers of water coming out all around.

The object is to keep the slurry, but the processing plant is about 2000m from the basin, we haven't found pump that can be mobile, fuel powered, and pump 2km. We tried adding water to the basin and pumping, but mixing the slurry in the basin is impossible and we just end up pumping water.

We currently dig, pump, dig, pump. However, the machinery has reached the limit of their reach, and when we attempt to go down the machinery gets stuck immediately. Have you used the floating road bed?

We're currently thinking of using a Geotextile with timber on top, then backfilling with aggregate. Anyone have any experience with this type of idea?

Can you auger it into transport trucks or conveyor belt. Or a tank where it can be stirred into a slurry you can then pump?

That's an interesting idea, the auger. Getting it out of the basin is secondary to trying to keep the equipment from sinking. If the floating road works, maybe we could use an auger to move the material up to haul trucks vice having them at the same level as the excavator. My biggest problem right now is getting a road/platform built on this mess that doesn't just sink into the muck/sluff off/etc. Have you used an auger/conveyer before? If so how much material did you move, and overall how efficient was it?

I worked at a Kansas grain elevator once. It had a 60,000,000 bushel capacity. They used augers and conveyors. They could unload a rail car with 200,000 lbs per car in minutes, all day long. It was always dry though.

No, I haven't. But I know the US Army has used a product like this in swampy areas and areas where wet clay acts like heavy grease.

Perhaps, you can use a drag-line to excavate.

No drag lines. "not economically viable"

Q #1: How large is this basin? Providing dimensions would be helpful.

Q #2: What is the current maximum water depth?

Q #3: Why is there a need to over-excavate the basin?

Is this a "tailings" basin at a mining/refining facility? Canadian or Alaskan Permafrost area perhaps????

My first thought would be to use a dredging barge of some type if the basin is large enough to accommodate it. Not knowing the details of the clay "slime", I first off would say if it's squishy like toothpaste, or worse, then the installation of a geotextile and aggregate most likely will not work, and any attempt to bring an excavator onto it would be a fruitless endeavor....your "roadway/work platform" and excavator will quickly sink out of sight (or get sucked down into the mire).

You may have to de-water the basin if at all possible and allow the muck to dry out, if you have the time to do so. Either that, or drive cofferdam sheetpiling and excavate out the interior with a clamshell, then pull the sheets and redrive in an adjacent area...ditto ditto ditto.

Anyhoots, I'll have to search through my US Army Corp of Engineers Engineering Manuals on effective excavation methods and procedures pertaining to Permafrost or Glacial Till, which I suspect that this material is. Hold one please.......

Explore the possibility of using a crane with suitably long jib, rigged with say, a 10 ton or higher capacity grab/clamshell to excavate.

Every road you build sinks, When they built roads in swamps, the base they used was logs staked width ways, and then laid the roads ontop of the logs. Allot of the roads were called corduroy roads.

I do know HDPE plastic geogrid used in conjunction with crushed stone aggregate subbase has been successfully used in the past by the USACE in swampy areas in order to build levees, construction access roads, and inspection roads in MS, AR, and LA, and several other locations elsewhere. When I was with the both of the USACE Vicksburg and New Orleans Districts we used it as a foundation stabilizing/reinforcing material. Before installation, you could not walk in the muck and waist high water....you'd literally sink out of sight and drown. After installation of the BIAXIAL geogrid, you could walk on water like the Lord (well, almost). The geogrid acts like a big snowshoe, sort of.

Look up Tensar geogrid, or other manufacturers under plastic geogrids. It may work for you. I must warn you that it is not cheap by any stretch of the imagination, but then again you get what you pay for: certain copycat manufacturer's offer cheaper and less performance driven products and you may end up with a total waste of $$$ and effort.

When in doubt hire a geotechnical engineer to come to your aid and solve the access problem......we here in the forum are hundreds of miles away and cannot see the actual insitu conditions that you are dealing with there.

I forgot to mention another thing.

Look for US Army surplus "Mo Mats". They are hard to find, but worth it. Used during WWII and thereafter to build roads and airfields in swamps.

Here's a good discussion regarding recent developments of Mo Mats:

http://www.almc.army.mil/alog/issues/JanFeb02/MS698.htm

[I forgot to include this in my previous posting....it's been a long tough day.]

When we de-silted dams in the outback, the water was never removed. It went a bit like this. (We got a local contractor who had the equipment and I got the job of being his navvy.)

He had a winch truck (Old WWII Blitz) that we would attach to the largest tree around.

On the winch was a 1 cubic yard dredge bucket with a hinged rear face that had a high pole (around 3 yards above the bucket edge.

Attached to the top of that was another smaller cable that extended across the dam to a willies jeep.

Once deployed, the jeep would drive away from the dam, this pulled the lever that opened the back of the dredge and allowed it to be towed into the dam where it sank until contacting firm material.

Once deployed, the jeep was put into neutral and the winch truck would pull the dredge through the floor of the dam and out onto the bank.

There was some finesse about how the dredge was deployed and aimed and how once full it "floated" on the bottom material instead of ploughing on.

No-one got wet feet, if a cable did break (And i never saw that happen ever) the other cable was available to recover the dredge. The direction the jeep ran determined where the next cube of mud was removed from.

When we needed a new alignment, we just moved the winch truck to another tree.

Effectively similar to a dragline, but no boom and highly mobile.

Contact some of the "old world" farmers over your way. They will probably know someone with the technology. We took around 2000 cubic in a few days.

we have used a large front end loader for cleaning muck from settling ponds. a dozer was useless.

Can you provide a photo?

What is composition below the basin?

What dimensions are you talking about?

I'd love to provide a photo, but for whatever reason I can't upload one.

I think we've solved the issue, for now. We laid regular landscaping fabric down (waiting on Geotextile/geogrid), logs on top of that (we didn't lash them together, we did only de-limb the bottom), then aggregate.

The "road" floats, and is reasonably stable. I think the geotext will help out greatly with stability, but the cheapo fabric is actually working pretty well.

This is a tailings basin, and it's about 1500'x1500' and between 20-50 feet deep.

A not too large float or barge made from lashed up drum. A water gun made with a gasoline pump. The produced liquid / slurry pumped thru flexible hose to an area designated as settling pond. Recycle the water to the water gun. Geotex may help you to build a dam in the settling pond, always higher. From the description I do doubt, you will suffer from water shortage, ever. Clay and silt eats up shaft seals in a hurry, so centrifugal types not relying on it are of an advantage.

thats the exact answer i was about to give except i would have mounted the nozzle of the water gun on the end of an excavator arm , positioning it over the job site and keeping the excavator on solid ground

How about a Hovercraft?

Option 1.

If the basin has a solid base, could you sink vertical posts with a load spreading base through the slurry to the base, then build a platform on/between the posts to support the excavator and receiving truck. You could design it so that the platform could be lowered down the posts as the slurry level drops. Build several of these around the periphery of the basin to progressively lower the slurry level until it is shallow enough to drive the excavator in at the edge and progressively 'nibble your way across the basin.

Option 2.

Alternatively you could build and anchor your 'cordroy' road down to the edge of the slurry and progressively nibble your way in with your excavator, to the extent of its reach, extending your 'cordroy' road as required, but not extending it into the slurry.

However you approach it I expect your progress to be slow but you will eventually get there - take it in manageable bites.

Two issues here. Site access and pit drainage.

You said that using logs didn't work. Did you lash the logs together. You don't want gravel on top of your log road.

Trenching didn't work. How about another deep hole (sump) adjacent to your work area (upstream on the aquifer) to relieve the water pressure in the soil. Pump the sump out to somewhere downstream. Work fast to get the blinding in.

If you have free access to lumber then use it.

Did you mention your location?

Just feed the coordinates into the next North Korean missile test.

In 1830 Robert Stephenson (of "Rocket" fame to all of you who know about the history of early railways) was building a rail line between Liverpool and Manchester. The route had go over several miles of of a peat bog known as "Chat Moss". His solution was to put bails of cotton onto the moss, covered by bracken with a top layer of shale. The rail line, without substantial structural modification, is still in use today carrying regular passenger trains and some 6000 ton coal trains.

When logging in a swamp, using trains to haul out the logs, long timbers(40 feet or more) were laid down in the muck,then the cross ties were laid across the tops.This made for a scary ride on the train, reminding one of a ride on the ocean, but it help up just fine. When leaving an area, the logs were removed and loaded on the last cars leaving, and reused at the next location.This left virtually no footprint afterwards, and complied with EPA requirements.

It is possible something similar would work in your case.

A note about the cotton bales:Unlike loose cotton, compressed cotton is virtually waterproof.Textile fires would smolder for months when a bale caught fire, because the water would not penetrate into the cotton.Then one day, a mill worker, tiring of the smoke, poured kerosene on the smouldering bale.It penetrated and extinguished the fire.This became a standard method of extinguishing smoking bales afterward,and is still the best way even today.

Hard to beat country-boy wisdom sometimes.

I know its expensive but freeze the ground, or slot either side of the basin with a dyke wall strengthening cutter, it slots the ground and mixes the spoil with cement which is fed back into the slot to form a wall, when you've totally enclosed the area excavate the basin, a third option would be to bore down to a depth that would allow you to pump out the water.

Bazzer

Mixing dry concrete will form a semi rigid mass that can be excavated.

Mixing in Schaeffer's #235 non-ionic surfactant and soil penetrant may help the water to drain and penetrate the bottom of the basin. I know it works to penetrate clay soils to reduce water accumulations above ground. The treat rate for crop irrigation is typically 1/2 to 1 quart/acre, at a cost of about $35/gallon.

Maybe the mixture of both will help. You could try a small area on the edge to see if it improves your situation before using it in larger areas.

Do you have access to a Hydro Vac pumping truck.? They work fast and have a long reach similar to Lyn's suggestion. When full you can transport to processing.

I really like to see a problem when trying to solve it. Any chance of some pictures and perhaps analysis of what we are dealing with?

My first thought is to bring in a small dredge on a small barge. Like they use in Alaska in rivers, etc. dredging for gold?

What about something like a concrete pump with a flexible drive mounted on the end of an excavator arm to be submerged in the slurry and pump it into waiting trucks....

This reminds me of cleaning out the flat bottom mud tanks on the oil rigs a few summer ago.

After the slurry sits for a few days all of the heavy material settles out and you end up with a soft clay like material with the density of wet concrete. The trick I figured out after busting my butt and back for 4 hours one day was to not pump the water off the top but instead get in with hip waders and start walking around and stirring things up.

Wow! a 4 hour back breaking shovel and scrape job could be reduced down to about 45 minutes of walking around with rake to keep it worked up as the vac truck sucked off the bottom of the tank! Easy quick and sort of fun!

Its a strange feeling though to walk around in something with a specific gravity similar to wet concrete but with the fluidity of motor oil.

The best part is we got paid by the BBL for most jobs and even at a slackers pace we still could move 2 - 3 times as much in a 12 hour shift as the other crews could.

The point is if done right more water and some basic stirring can make things worke a lot better instead of worse!

Nice story mate.

Work should be fun.

Play safe.

The real funny part was the two managers of the company I worked for busted me down from truck driver at $15 an hour to swamper which was basically the super VAC truck operators grunt helper.

The idiot managers thought that swamper's pay was only $10 an hour and they figured they could get me to quit by making me do the remedial labor jobs at low pay. Unfortunately for them it turned out swamper pay was $20 an hour plus a per BBL bonus with most rig jobs for one company we dealt with.

I liked that job! I traveled around met lots of interesting people on the rigs plus learned a bunch about the rigs themselves and the way they ran plus made a boatload of what I considered easy money!

Well I did that for about two months then the two idiots found out they gave me a better job instead of worse. Then they put me back in the trucks again and tried to set me up for a couple of fireable offenses that didn't stick (Illegal load hauling and a wrecked truck. Witnesses and mechanics said otherwise)

My paperwork trail plus multiple third party witnesses made my story add up while theirs didn't. The big bosses overrode their excuses for firing me and sent me back to work with a pat on the back and an all around thanks for being honest!

I went home and never returned. A few months later one of them was fired and the other was raked over big time and I got an undefined mystery bonus check in the mail (minus taxes of course) one day from the head office around that same time frame.

Good for you.

...and they all lived happily ever after.

All,

In the event that someone someday has the same problem, I'll post what worked for us and what hasn't.

The background is that this is a 40yo tailings basin in Northern MN. We want the tailings to process, but ran into the posted problem. We tired Geotextile fabric and it failed. The material just "oozed" up around the fabric/aggregate combination as the equipment compacted the ground. As it oozed in, the ooze mixed with the aggregate and we were back to square one.

So thanks to a great publication by the Scots (http://www.roadex.org/uploads/publications/Seminars/Scotland/FCE:SNH%20Floating%20Roads%20on%20Peat%20report.pdf) we're up and running. Forewent the Geotextile, and just put the timber (poplar/pine, and transverse to the road obviously) on the saturated tailings and covered with aggregate 18-24" and it's holding fine. We dug drainage ditches along the sides outside the berms but I'm not sure they're even necessary.

Thanks for all the help and suggestions.

-Sam.

Thank you sam

Are you part of the iron recovery program in MN? Is your product used in the Kobe/Midrex nugget process?

Yes, and yes. Please PM me for more info Sir. Though we shan't be getting too specific. -Sam.