The Wallap method is to ignore the active thrust below excavation line due to soil arching (this is done by setting Ka to 0) and then to factor down the passive resistance as each post is only receiving its passive pressure from a 3d width of soil in front of the post.
However when doing a hand calc as a check, adopting the typical cantilever wall approach doesn't work as its not a continuous wall below the excavation line. Wallap gave an embedment depth of 2.7m for 1.4m height with a Fos of 2. I have had this checked by a senior engineer and he confirmed it. I have done a king post analysis in Wallap and followed the methodology provided and it works ok. Thanks SRE - thats what i was assuming too.
