FixedEarth,
Thanks for the quick reply. My design spacing is 7 feet and I tried with 6 feet too. I considered the surcharge from all three tiers. It is a single tie back anchor design. I attached a rough sketch of the cross-section...
I am working on a 21 foot(above ground surface) tall solider pile wall with tieback anchors. The wall will support 3 concrete tier walls. I considered my first anchor location at 10 feet from the top of the soldier pile. After the completion of hand calculations, I ran a global stability program...