



Calculate Slip Plane Angle And Depth of Crack For
Soil: 
Use the calculation below to perform trial and error calculations to find the
slip plane angle (SPAng) and depth of crack (dc) for cohesive soil with an
inclined slope. For cohesive soil with a horizontal slope or noncohesive soil, SPAng will be equal
to the first run of the calculation below. 

Calculation: 

Designer/Checker: 



Input: 




(Note: All input Metric units are converted to English units
for the equations below and then the output English units are converted back to
Metric) 

The following calculation will calculate the slip plane angle for soil and the
depth of crack for cohesive soil. 
For the first trial enter 0.0
for SPAngEst below: 



Angle of backfill slope, (AngB  degrees) 

Estimated Slip Plane Angle,
(SPAngEst  deg)
SPAngEst = 45deg + AIFd/2 

Height of retaining wall (H  ft or m) 

Density of soil (d  pcf or kg/m^3) 

Developed angle of internal friction (AIFd  degrees)* 

*AIFd = Arctan(SMF * tan AIF) 

Cohesion of the soil * SMF (cd  psf or kPa) 

Soil surcharge (V  lb/ft or N/m) 

Typically the Strength Mobilization Factor (SMF) is 2/3 











Output: 

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Depth of crack, dc = 

Calculated slip plane angle, SPAng = 






