GGU-RETAIN: Analysis of mobilised passive earth pressure using global safety factors
In accordance with the EAB R 9 and Weißenbach (Geotechnical Engineering Handbook, Volume 3, 2001), two cases must be distinguished:
Case 1
The vertical forces acting downwards are relatively small.Case 2
The vertical forces acting downwards are greater than the vertical components of passive earth pressure determined using a negative angle of wall friction.
In Case 1, Weißenbach (Geotechnical Engineering Handbook, Volume 3, 2001) gives the following relationship:
ηv = (Pv + Eav + Cv + G) / Epv
Eav = vertical component of active earth pressure
Cv = vertical component of the counterforce C for toe fixation
G = self-weight of wall
Pv = permanent external loads (including vertical components of anchors)
Epv = vertical component of passive earth pressure
In accordance with the EAB, Cv is always determined as 1/3 · φ. The EAB gives a safety factor of 1.5.
In Case 2, Weißenbach (Geotechnical Engineering Handbook, Volume 3, 2001) gives the following relationship:
ηv = Qg / (Pv + Eav + G)
Qg = vertical ultimate bearing capacity of the wall or soldier piles
Qg can be determined pursuant to DIN 4026 or DIN 4014.
Further useful information relating to verification of V can be found in Weißenbach (Geotechnical Engineering Handbook, Volume 3, 2001).
If the wall toe is bedded, Epv is determined from the positive subgrade reactions and the angle of wall friction.