Retaining wall over obstructions 1

[mralhasani]

Hi i am working on a project and i need some advice on the choice of retaining wall

I have a site that has a old victorian pipe 12m below ground level and that is 4m wide. I need to design a retaining structure over this pipe. The soil is london clay with the water level 4m below ground level.

I cant diverty the pipe because it is rather old and made of cast iron.

I have ruled out using king piles because the water table is rather high.
Any suggestions on what retaining structure i can use without disrupting the old pipe??

 

[Geostructsparks]

Can't make much of a recommendation without knowing the height and construction method of the wall. Concrete cantilever footing?
Also, is there existing soil on the upslope side of the wall (so there will be little new surcharge. e.g. are you replacing an existing 2H:1V slope with a wall), will the wall retain new fill, or retain new cut.
For a pipe that's been there 100 - 150 years and 12 m depth, I'd be much more concerned with the overall stress change due to fill or cut than the small stress bulb created by the footing itself. As long as there's such a thick cushion of soil over the pipe, I imagine an additional stresses will be arched around the pipe due to the 100 - 150 year-old compaction effort (assumed to be low). This backfill could however result in added settlement of the wall and fill over the pipe.
Can't say more than that until I know more...

 

[oldestguy]

A procedure that involves placing a concrete slab over the area of the pipe, with some possible fill that is compressible was developed by an old engineer in Iowa, USA, by the name of Spangler, long dead.

I have used this on a few jobs.

Check this paper out.

http://pubsindex.trb.org/view.aspx?id=801079

After this slab is built, you probably can use an ordinary retaining wall which rests on earth.

 

[oldestguy]

I see I was wrong with the name of the "inventor". Spangler was there after the original engineer who checked out culverts. His name was Marston. Spangler carried on Marston's work.

See this thread: 158-259207

And do a search for "Imperfect trench"

 

[msquared48]

mralhasani:

I have never heard the term "King Pile".

What do you mean by this?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[mralhasani]

Thanks Oldest guy!!

msquared48:

King pile is also known as soldier pile or various other names.. Its installing steel or wooden I beams and putting planks between the beams.

 

[msquared48]

OK. Thanks. Just different terminology.

Any reason why Augercast pile to either side of the 13 foot wide pipe would not work - drilled as opposed to driven as driving pile could damage the old pipe?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[mralhasani]

I thought about making a secant pile wall using a cfa auger. I agree that using a auger would be a better choice than driving piles since the vibration would be minimized.

If i were to use an auger are u suggesting to create a secant pile wall?? How can i maintain continuity for the wall over when passing over the pipe?

Can i create a secant pile wall by example driving 12m piles all around the site but when i reach the pipe i drive 10m piles. Can this work?

 

[msquared48]

I had envisioned you using a free standing, yielding concrete retaining wall over the area of the old pipe, but relying on an augercast pile system to bridge the area over the old pipe. I was thinking of the footing for the concrete retaining wall to be supported by an augercast pile system of vertical and batter pile as needed.

The main design problem I can see here would be the differential deflection between the piled and non-piled portions of the retaining wall.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[BigHarvey]

CFA augers are not rigid enough to build a nice secant wall. With a rig equpped with a double rotary head ( eurodrill ) you can construct temporary cased auger piles without deviation because of the rigidity of the temporary casing. Look on the web vor VDW drilling method.

 

[six06]

I dont see why not using the soldier piles and pump the water. If its clay, you have the permeability advantage and would give you plenty of time to pump the water.

 

[csd72]

The question I would ask is:

Are you actually adding any additional load to this pipe 12m down?

If the soil is already at a similar height to the top of the wall then the answer is probably no.