How to overcome sliding due to limited heel width 1

[PlasmaStruc]

I am facing a problem with a limited heel width (about 0.5m) of a 4.6m tall retaining wall. I've got plenty of space on the toe side. Sliding is the critical condition. I have considered a shear key, but the effectiveness of the shear key seems to be not impressive. Appreciate your advice. Thanks.

 

[BigH]

Can you post a section? I'm not seeing what the problem is as you have plenty of toe width - Use a gravity wall - either mortar rubble or a MSE wall - I am presuming that the "wall" doesn't have to be in a particular location.

 

[PlasmaStruc]

The section of the wall is as given below:

 

[Ron]

Your wall shows a shear key. Like BigH...I don't see the problem here.

 

[BigH]

In looking at your sketch - why do you have a problem with the heal? Are you cutting into the soil behind? How do you you expect the soil behind to stand up? Or, is the land somewhat flat and you are building the wall to raise grade on a slope? As you don't show the original ground line and what it is you exactly want to do, it is difficult to give short response. I am assuming that there will be some added fill behind the wall (make sure it is free draining so that it does not create hydrostatic pressures behind. The surest way, given your "long" toe is to add more weight to the toe. In your case, why not just fill in the triangle from the toe point to the crest with concrete (expensive, perhaps) or by placing rock fill on of the toe (or preferably mortared rubble) to increase the weight on the toe side of the back of the wall - won't need a key then.

 

[PlasmaStruc]

Thank you all for your concern to my problem. My intention was to post the problem in a simple manner. But I see that I need to tell you more details for you to help me. this is the case:

This is actually a retaining wall and a foundation to a super structure. The superstructure is 3 storied steel building. Columns are spaced at 4m intervals along the wall. The wall is 36m in length. I have isolated in 12m intervals for thermal shrinkage issues. The loads from the superstructure can be ignored for now, because the sliding is critical just before the superstructure is erected. During construction the is doubtful about the construction methods, and the passive pressure above the footing level is not reliable. So I have to ignore the passive pressure. The safe bearing capacity of the soil is 175 kN/m2.

I have to consider active pressure with a coefficient corresponding to soil at rest condition, this works out to be 0.5. Saturated soil unit weight is taken as 20 kN/m3. So the lateral pressure on the wall is 10 kN/m2. In addition, on the uphill side a 3m wide road will be laid. Can be assumed as a 12 kN/m2 imposed pressure.

The existing ground level is the level indicated on the uphill side. On the toe side, the ground floor.

Thanks in advance.

 

[Guest262653]

So, this is a basement wall, right? If that's the case, sliding is usually solved by using grade beams connecting the wall footing to the building foundations and to the wall on the opposite side.

 

[BigH]

Nothing is simpler than a good sketch drawing with a few words.

 

[PlasmaStruc]

@avscorreia, Yes it is a sort of a basement wall. Its is above the water table. I was in the view that the use of grade beams will be effective only of the next column foundation ( to which the grade beam is linked to) should be able to take the sliding force.

 

[Guest262653]

Can't you connect it to the other retaining wall on the opposite side with a grade beam?

 

[hokie66]

Is the wall braced at the top by the first suspended floor? If it is, and the basement floor also braces the wall, I can't see sliding being an issue, as it will not be a cantilevered wall in the finished structure. If it is cantilevered and does not go up to the suspended floor, then you have an issue with the columns, which should not be cast monolithically with the wall, as the wall will rotate, and you don't want the columns to rotate.