Calculation of earth pressure coefficients and earth pressures

• Horizontal earth pressure coefficients are calculated according to EN 1997-1 Annex C 2. By using this method, it is possible to calculate coefficients of horizontal active and passive earth pressure for variable soil conditions, terrain inclination, construction inclination and soil strength parameters.
  
  
  
  • Partial coefficient of horizontal earth pressure for vertical loading on the surface:
  
  
  
  

• Partial coefficient of horizontal earth pressure for cohesion

• Partial coefficient of horizontal earth pressure for soil weight 

• In the formulas (1) - (3), b is the angle from the horizontal to the soil surface (positive when the soil surface rises away from the wall),Q is the angle between the vertical and the wall direction (positive when the soil overhangs the wall), f is the angle of internal friction and KN is the coefficient of the normal earth pressure acting on the wall from a unit pressure normal to the surface. Further detail can be found in EN 1997-1 Annex C 2.

• The inclusion of the mobilisation of earth pressure in front of the wall is optional. Height of the soil in front of the wall hp is an input parameter. User has 2 possible alternatives:
  
  
  
  • No earth pressure in front of the wall is taken into account,
  
  
  
  
  
  
  
  • 1/2 passive earth pressure + 1/2 earth pressure at rest 
  
  
  
  

Check wall stability

• Degree of utilization in the case of toppling is calculated according to the formula (5), where MED,dst and MED,stb are destabilizing and stabilizing moment around the construction toe. 

Safety factors according to EN 1997

• It is possible to use 9 different partial factors:
  
  
  
  • gG- partial factor of safety for the unfavorable permanent  load (Action),
  
  
  • gG,fav- partial factor of safety for the favorable permanent  load (Action),
  
  
  • gload - partial factor of safety for the surface load - for higher versatility treated as separate factor (Action),
  
  
  • gRh- partial factor of safety for sliding resistance (Resistance),
  
  
  • gRv- partial factor of safety for bearing resistance (Resistance),
  
  
  • gangle- partial factor of safety for the angle of internal friction (Material),
  
  
  • gcohesion- partial factor of safety for the cohesion (Material),
  
  
  • gweight,soil- partial factor of safety for the soil unit weight (Material), 
  
  
  • gweight,wall- partial factor of safety for the wall unit weight (Material).
  
  
  
  

• Appropriate combination of partial factors can be chosen for required design approach.


• Earth pressure in front of the wall is taken as favorable action.