foundation for L shape retaining wall

[Andrew88]

Hi all,

Could you please have a look at the attached sketch? I am looking for the way to design strip foundation underneath this wall. The forces are given there and are as follows:

Resultant sliding force: 10.3 kN/m
Resultant destabilizing moment about point A: 4.2 kNm/m
Vertical resultant load: 6.3 kN/m

All above doesn't include forces/moment from the strip foundation, only from walls.

Would it be okay if I were to calculate all forces about the tip of the foundation with factor 2-3? If I were to make it wide and deep enough I would get large counter force on decent eccentricity. Is there a simpler way or better approach? Should I consider the anchor?

Thank you,
Jedi

 

[msquared48]

There are a lot of good references to address the design such as Bowles.

A couple of comments though.

H acts 1/3 up the wall from the base.

Forget the anchor and use a concrete key lug below the wall.

To prevent over stressing the soil as this a very inefficient design, the base foundation length of the wall will be close to the height of the wall.

Mike McCann, PE, SE (WA)

 

[Andrew88]

Thank you for the reply. Please have a look at the new sketch.

I am in the situation where I can't change this design. As you can see its stem will be faced against the brickwork with a small cavity that will be filled with a concrete/grout. I assumed that this will be bonded together so the brickwork and concrete in the cavity will act on a lever arm against the overturning moment coming from the pressure that is exerted on brickwork through liquid.

I calculated all the moments about point A and the resultant forces and moment are shown. Unfortunately, I ended up with a large sliding force so now would like to have the plinth to carry on the shear force (sliding force) that the base/ground friction force can't take. The plinth is like a ring beam so my idea would be to design it to take all loads. Can I think about it as a rectangular beam in torsion? Force couple coming from the tension in the anchor and the resultant of compressive stress between toe and plinth? Here I will make it so that the bolt will take the shear force.

Thanks again,

Jed

 

[dik]

and have your footing going the other way, so the soil on top is resisting overturning.

Dik

 

[Andrew88]

This ground level is as the top of the plinth level. Please think about it a small above ground tank that has poor existing walls (brick) and precast walls are to strenghten it. I really can't change it so am looking for a way to design the ring beam (plinth) to resist it.