NCMA Seismic Analysis with high PGA value

[jagti]

If i input say 0.42 PGA value in NCMA design limits max slope above wall (6H: 1V) when doing Seismic Analysis. .

The grading plan from which wall height is picked indicates a 3H: 1V slope above wall.

Increasing the wall height to match the limiting slope (6H: 1V) to satisfy Seismic analysis will require changing of grading drawings.

I have already used high friction values for infill,retained & foundation soils.

Is there any other way to get around.

 

[Doctormo]

Which version of the NCMA program are you using? SRWall4 is the most recent version and may provide more latitude in the seismic analysis based on displacement Kh values and a different internal method. Be careful with your assumptions as this part is subject to many questions.

The Mononobe-Okabe equation solution used by NCMA does not work when PGA, back slope, and phi angle exceed the limits of the equation (square root of negative number for phi - backslope - aTan(Kh)).

That being said, high accelerations and steep slopes never solve very well by equation or slope stability analysis and require a more customized approach to the structure design. Displacement analysis, trial wedge analysis, and slope stability analysis are some of the tools used to analyze these conditions.