Retaining wall and a pool

[kubuton]

I’ve been asked to design a masonry retaining wall that will be used to partially enclose an above ground residential swimming pool. The retaining wall will range from approximately 6 to 9 feet in height. The pool contractor would like to use the back of the retaining wall as his shotcrete form. He intends to place #4 rebar, both horizontal and vertical, in the middle of a 12 inch thick shotcrete pool wall.

How much load should I expect to be transferred from the pool wall to the retaining wall? I’m thinking that I need to use an EFP of 62.4. Thoughts anyone?

 

[hokie66]

Are you talking about the construction (form) pressure from the shotcrete or the water pressure from the pool? As you mentioned 62.4, I assume the latter. But is not the 12" concrete pool wall the structural element which retains the water? A section through the pool would help in understanding your problem.

 

[oldestguy]

Any below freezing temp in your area and ice potential? That pressure gets darn high. Bubbler systems can work to avoid it. Is saturated earth going to affect foundation support? Any joints that may leak?

 

[kubuton]

hokie66 - In theory the pool wall will be the structural element though I expect that some of the load is transferred to the retaining wall; how much is the question of the day. I haven’t sketched up any sections yet.

oldestguy – there is some potential for below freezing temps (central NC). I expect the shotcrete to eventually crack. Saturated bearing soils shouldn’t be an issue if the pool contractors drain works as planned.

 

[oldestguy]

Splashing by users gets all over the area.

 

[hokie66]

"I expect the shotcrete to eventually crack". You need to provide sufficient flexural and crack control reinforcement to prevent leakage from the pool. A pool built with adequately reinforced 12" concrete walls should not leak.

 

[kubuton]

Hey guys, I appreciate all of the input. The pool walls will be contractor "designed", no. 4's horizontal and vertical. That gets me back to my original question. Now that I am a day into this, I'm hoping that I don't have to design for an EFP of 62.4 pcf, since the pool walls should provide support. Would you think it reasonable to design for say 30 to 35 pcf?

 

[hokie66]

Without a section, I really couldn't comment about design loads on a retaining wall which may or not be retaining anything. But I don't use the concept of equivalent fluid pressure.

 

[kubuton]

Wall will range from 6 to 9 feet tall.

 

[oldestguy]

I'd want to see the credentials of the pool guy, specifically his PE certificate. His guarantee in writing also needed. The block "wall" and brick facing appears to function only as a form to which the shot-crete is applied.

 

[hokie66]

Your section should at least show the reinforcement in the correct face, rather than centrally located. In addition to this top of wall section, the critical thing is what happens at the bottom. I assume the pool wall is cantilevered off the pool floor. The block wall does look superfluous, if the block and concrete are the same height.

 

[RHTPE]

The load against the pool wall varies from 0 psf to (62.4)(pool depth) at the bottom. A 10' deep pool wall will see a load varying from 0 psf to the water surface to 624 psf at the bottom. Simple hydraulics.

Design accordingly. Or, toss it back to the pool contactor's P.E. and let them to the design.


Ralph
Structures Consulting
Northeast USA

 

[FixedEarth]

In the past, we have recommended crushable material between the retaining wall and the pool. This way, when the wall deflects, it doesn't push on the pool.

http://www.soilstructure.com/