Retaining wall with slight complication

[iandandav]

I need to build a retaining wall about 7-8ft high. There is an added complication of a spring letting out water in three places. It is a constant stream coming out from between the layers of sedimentry rock. I have a few questions about building this wall.

Whats the best way to join it to the existing wall?

Is a thickness of two standard dense building block sufficient at the base (largest face up) and rising half the height of the wall, then single layer of blocks?

How deep for the foundation, and best mix for the concrete?

At the moment Ive dug channels for the spring bringing them out and joining them as a stream in front of where the wall will be. If this is the best location for the water, should I channel the springs through the foundation or dig it deep under the foundation.
or would it be best to have the water channelled behind the wall?

Some pics to show the situation
Overall view. The site slopes up from left to right and bank is about 8ft high

Arrows show the water emerging from the rocks in 3 places. Ive channelled them forward and they join to form a stream.

The red section shows where I want the base of the wall to sit. The crosses show where I would like to join it to the existing wall

Close up of the regon where the retaining wall will join to the existing wall. Also you can see where the stream leaves my property and follows a natural or man made route under the neighbours concrete drive. (neighbour doesnt know the how the water was dealt with when his drive was put in place)

Thank you [/img]

 

[RonnyRaygun]

8 feet is pretty high...you should seriously consider getting it designed in RC or similar by an SE. I don't think what you are describing would last five minutes...
You've got sliding, overturning, bearing, and bending to contend with...quite a complicated process to get right in a scenario such as yours.

 

[theoldun]

SE designed RC with massive found. Pay no attention to any thing any one else tells you except chart SE.
oldun

 

[freddiemercurystwin]

Concur with Ronnnyronronron and old duffer.

 

[hotrod]

Aye. That's one hell of a gradient - ditto the advice above, get an SE onboard to spec the job.

 

[ChapiTheBricky]

in my opinion that is as big a job as a retaining wall gets, you need to install a drainage system, get an engineer to design something, fyi i'm doing a little retaing wall (1m high) in a few weeks time and the first 140mm of that is 18" thick

 

[ChapiTheBricky]

p.s. you'll need to put in an impressive shoring or remove lots of soil before you consider excavating for founds.

 

[iandandav]

Thanks for all the advice.