Sheet Pile Wall with Anchor Tie Rods (Turn and Buckle) and Deadman

[X-Wing]

Hi everyone! I am designing for this certain project, and the plan needed/suggested to have an anchor deadman. I was given a force per linear meter of wall that the anchor will be restraining, and then I designed the deadman, the waler, the tie rods, and the plate.

My main question is the tie rods, because what came out from my design is that a 50mm tie rod is needed per deadman anchor, that was placed every 3.2m. To reduce the size, I instead use two tie rods, so I came up with 2-25mm. Is the tie rod diameter too big? considering the spacing of only 3.2m (for the deadman) and a unsupported depth of 5.5 meters of sheet piles (including the scour depth)? the length of piles is 12m each.

 

[PEinc]

We can't answer your question if we haven't seen the plans, soil borings, geotech report, specs, etc. However, tie rods come in steel with different available ultimate and yield strengths. You may need a 51 mm rod but we don't know what load or strength steel you are sizing it for. Most commonly used for deadmn tie rods are Grade 75 threaded bars (Fy = 75 ksi) and Grade 150 bars (GUTS = 150 ksi). Grade 270 strand tendons could also used where the ultimate strength is 270 ksi. Check on-line for available threaded tendon bars and/or strands from DSI, Williams Form Engineering, SAS Stressteel, and Skyline Steel.

http://www.PeirceEngineering.com

 

[X-Wing]

Thanks for the reply sir, fortunately the design was revised and my original scheme was used (without use of deadman)

For the knowledge sake, can we used tie back anchors that are not on rocks?

Very Truly Yours,

- andru18

 

[PEinc]

Tieback anchors can be installed in soil or rock, depending on the type of anchor and installation method.
Helical anchors are installed in soil but cannot usually or economically develop the same capacity as a drilled and grouted anchor.
Tieback anchors can be drilled or augered and grouted into soils.
Tieback anchors can be drilled through soil overburden and into bedrock.
Tie rods are connected to deadmen which usually are made from steel sheet piling, concrete, timber drag piles or driven piles.
The type of anchor usually depends on the required design load, ground conditions, and available access.
If you have competent soils, you do not necessarily need to install the anchors into rock.

http://www.PeirceEngineering.com

 

[hokie66]

2-25 mm diameter rods only provide half the area of 1-50 mm diameter rod. Perhaps you knew that.