Stacking retaining walls

[hotmailbox]

Please see the sketch below and discuss:
The wall #1 was designed for retaining height H1 and 1:1 slope backfill. All good. Now the client wants to build retaining wall #2. Technically we'll remove a decent soil mass behind the wall #1 to build the new wall and think there is no extra load or surcharge on the wall #1. Is this true? The city asks that the wall #1 shall be design for retaining height of H1 + H2 or the surcharge from wall #2. What do you think?

 

[phamENG]

I think the city is correct.

 

[Celt83]

The rear wall alters the stabilizing soil mass over the wall# 1 heel in my opinion.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[hotmailbox]

Don't you think the slip surfaces for wall #2 would be inside the governing slip surface for wall #1?

 

[geotechguy1]

The city is right.

To design them 'independently' you'd want a separation distance of twice the height of the lower wall (and then you would still need a global stability check).

 

[kieran1]

How do you intend to build this?

Kieran