Cantilever Retaining Wall - Stability against sliding

[18061951]

Due to the presence of very very aggressive soil my cantilever retaining wall base (for a water retaining reservoir) is founded on waterproofing membrane installed over the blinding (PCC). To provide stability against sliding a 1.0m deep shear key is provided.
I have calculated the safety factor against sliding by considering soil-soil friction along a plane from the toe of the base to the bottom of the key (key is at the heel of the base). I did not consider the passive pressure at the key. Even then it is safe. Another engineer says that it will not work because the base will move to some distance before satability is acheived. My problem is this that I may not alloe movement more than 10mm. Because a considerable movement will put the movement joint in jeopardy which may lead to leakage.
Please suggest what is the best solution.

 

[JedClampett]

I hate to put it bluntly, but the other engineer is wrong. He may think that you are considering the passive pressure on the key in your calculation. Passive pressure requires some movement before it is developed.
If your calculation is correct, the wall won't move.
Also, if the wall is water retaining, you should be using centerbulb waterstop in any expansion (movement) joints. These waterstops can move quite a bit before they tear. Some of these with large centerbulbs or tear strips can move over an inch and not leak.

 

[Focht3]

Hmmm,

A movement of 10mm isn't much. (About 0.4 inch for us non-metric folk.) How tall is the wall? What kind of a pressure distribution did you use to model the soil behind the wall? What is the theoretical pressure distribution beneath the footing?

How much rotation of the wall can be tolerated? (Consider rotation of the top of the wall into and away from the basin.)

If the soils are "very very aggressive" (active?) then you need to consider the potential heave that may occur from water sources other than your basin, including seasonal effects. This may cause differential movement across the joint that far exceeds 10mm.

And the wall will move. The only question is "How much?" Your postings don't give enough information to evaluate your problem.

 

[jheidt2543]

18061951,

You also don't mention if the waterproofing membrane runs under the retaining wall footing. If it does, doesn't that affect your coef. of friction?