GGU-STABILITY: Passive earth pressure

If the circular slip surfaces in the resistance area are steeper than 45° - /2, the passive earth pressure is to be used, in accordance with DIN 4084. The DIN 4084 suggests a simple earth pressure calculation for consideration. The GGU-STABILITY program takes a much more flexible path. In the appropriate areas, the geometry of the failure body is altered, in line with the demand 45 - /2 as maximum. The slice width is kept. If necessary, the user-defined number of slices is increased. If a soil change occurs within the passive earth pressure body, with a change in friction angle, the geometry will be adjusted accordingly. During numerical evaluation of such a failure body the slice relationships used in the DIN formula are kept. Additionally, however, it is to be considered that the normal force in the slice foot now creates a moment around the centre-point, which is not the case for pure slip circles. For changes in the friction angle within the slip body, a change in the lever arm of the tangential force T_i around the centre-point must also be considered. This program concept is much more flexible than the approach using a substitute earth pressure force, as complicated slope geometries can be much better assessed. Slip bodies with a passive earth pressure wedge are shown with a third radius.

Remark:
The demand of the DIN 4084 to incline passive slip body areas with a maximum of 45° - /2, is strictly only correct for level surface.