Design of a 10m cantilever wall 2

[kellez]

This is the design of a 10m cantilever wall which i was assigned to check and confirm.
From my calculations i found that the wall is failing in sliding in the seismic loading.
I want to take this step by step with you guys just to get your advice, since i am in a bit of a conflict with the engineer that actually designed this.
Below are my own calculations.

As you can see i am using Rankine for now since i am not sure how to apply coulombs on a cantilever wall.

My main concerns about the parameters used are:
1) Angle of friction of backfill - too high, they are not conservative at all
2) Angle of friction of base soil- too high, they are not conservative at all
3) Angle of ground rising above wall - this angle may not be achieved and/or the soil at the edge will not be compacted enough due to the difficulty of the slope.
4) Unit weight of backfill is a bit conservative so that one is ok

I will first carry the calculations with what they assumed for the parameters and then start making changes.

First step is the Total Sliding force shown below

 

[Obregon]

Too tall for a cantelever wall without some kind of ground reinforcement. I believe soil nailing is the most practical and safest way to go.