Drainage Behind CIP Concrete Fascia Wall

[EngInternational]

I am reviewing a design of an 8m tall "L-shaped" concrete fascia wall (i.e., no heel just at the from of the wall) which is to be cast directly against a cut vertical limestone rock face. The rock is fractured enough to allow water to seep behind the wall. The wall has numerous weep holes spaced vertically and horizontally, but no granular fill or drainage sheet between the rock face and the wall. My concern is that there is no direct "path" such as a granular fill or a drainage sheet to direct the water at the back of the wall to the weep holes. The wall is NOT designed for any hydro-static pressure. Is my concern valid?

Cheers.

 

[JedClampett]

Yes.

 

[msquared48]

Very.

Mike McCann
MMC Engineering

 

[EngInternational]

Thanks very much for the replies.

A bit more background: The project is in a rocky area in the middle east and the local engineers say that casting direct against the rock is a typical construction methodology. It is one of those, "we've been doing it like this for 20 years...who are you to tell us we have been doing it wrong" situations. Still it "feels" wrong.

Is casting directly against rock ever "ok"?

If the design added, say, a 30cm gap behind the wall, filled with coarse material, the problem is that installing the formwork behind the wall, they say, may be difficult. And the site is very tight, so not much more room to move the wall out. How much room is needed for formwork erection? This doesn't seem that difficult a problem.

Can anyone point to a case study of a similar situation with drainage...you know...picture...1,000 words....

One more thing: if the rock is stable vertically, and wall is cast against it, should the wall be designed for some nominal lateral load, other than water pressure?


Cheers