Retaining wall supported on single pile

[AniMhj]

Dear everyone,
I want to design a retaining wall supported on single pile.
Can anyone give me tips on how to design the wall and pile?
Is there any book for the reference?

 

[BridgeSmith]

That should be fairly straightforward; not much different than a sign on a single post...with larger loads.

That said, if you'll post a sketch of the configuration, I'm sure you'll get some useful guidance.

 

[JoelTXCive]

I half-designed one several years ago, but the project changed so I never finished.

My concept was to do a deep grade beam supported by drilled shafts.

I then calculated the overturning moment loading per foot of the wall and calculated a tributary moment going to each drilled shaft. I think my wall was only ~10ft tall, but the moment gets large pretty fast. I would have used L-Pile for the drilled shaft embedment design.

It helps to have a deeper grade beam for two reasons:

1) Resist all the torsion.
2) It allows you to get your vertical wall bars fully developed into the grade beam; and also get your drilled shaft bars fully developed into the grade beam.

 

[AniMhj]

My wall is 4.2 meter high and base 1.5 meter.
I am getting factor of safety against sliding of 0.85 and factor os safety against overturning as 0.6 which are very low. I want those safety factors to be more than 1.55
I am trying to use the pile to satisfy these conditions.
I have attached the sketch of my problem.

 

[Enhineyero]

You need to follow the load path, how do forces get transferred from the wall to the pile? You can omit the base footing as it doesnt do anything, assuming base is supported by a single pile.

Most common way to build this is to extend the pile all way to the top of retaining wall to supported the concrete walls, concrete wall will bend (similar to a slab/beam) and transfer lateral loads to piles. Piles will resist the lateral loads using the soil below the base of retaining wall (think passive pressure/cohesion). The deeper your pile below the base of the wall, the higher the resistance. This is how most basement walls are built (i.e. bored pier and shotcrete).

 

[HTURKAK]

I do not know if other alternatives are applicable or not ( such as increase the base ftg length to 4.0 m, extent the ftg to the back side to get wt of soil for resisting OT and sliding ..)

If this is the only option, i will suggest you to use bored piles with dia 400-500 mm and two rows at the toe and heel with a staggered manner. The spacing of piles could be around 4.0 m

My opinion.
...

He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[Brad805]

We have done this. The leg in the retaining wall is not needed, but you will need a buttress in the wall to achieve a moment connection between the wall and the pile. Then you need to design the pile for the moment in addition to the gravity loads.

 

[BridgeSmith]

If it's an option, the simpler way would be a sheet pile or soldier pile wall.

A CIP wall on a single row of piles, especially vertical steel piles, is going to be an expensive option. The toe does next to nothing to provide resistance. I assume having a heel is not an option? What about a row of battered piles closer to the front of the footing? Even moving the one row of piles towards the front of the footing would improve things significantly.

 

[AniMhj]

The base of slab cannot be extended more than 1.5 meter. This value is fixed as per site condition. The heel cannot be extended as this lies in other's property.
I have designed the pile considering the additional moment to stabilize against overturning by the tensile force multiplied by the lever arm (i.e. distance between toe and pile center). Is this correct method?
Also, the wall rests on the rock foundation (Sandstone). The drilling of pile is also not a good solution. Is there any good solution?

 

[Smoulder]

Rock anchors are easier to drill. Combine with trench into rock if can't install anchors at the angle needed for them to work on their own.

 

[BridgeSmith]

With sandstone at a shallow depth, I would suggest drilling holes and grouting steel piles for a soldier pile wall.