Slope Stability Analysis
Designing a structure according to EN 1997-1 essentially follows the analysis of limit states.
Load reduction (DA1, DA2, DA3):
Loads acting on a strip are reduced in the analysis by partial factors. Depending on the inclination of the slip surface the program evaluates whether the gravity force acting on a given block is favorable or not. If the favorable action of force is greater than the unfavorable one, the program adopts the favorable coefficient. Based on that the weight of block W is pre-multiplied by the partial factor for the permanent load.
Determining whether the force action is favorable or not
For input surcharges, the program first evaluates whether these act favorably or not, and then pre-multiplies the overall load by the corresponding partial factor.
Reduction of material (DA1, DA3):
Parameters of soils are automatically reduced by the corresponding partial factors.
Reduction of resistance (DA2):
Resistance on a slip surface is reduced.
Calculation of slope stability according to DA2 or DA1 (comb. 1) using total parameters gives very unrealistic results. These are caused by a different reduction of the self-weight of massive (favorable and unfavorable). If adopting the above mentioned approaches we recommend to adjust the partial factors manually (i.e. increase the partial factor on resistance on the slip surface and decrease partial factors on load actions).