GGU-RETAIN: Area loads
Up to 20 area loads can be positioned on the active side at any height.
The slip surface angle for the active earth pressure resulting from the self-weight of the soil is adopted for analysis compliant to DIN 4085.
When there are several soil layers, the program moves from layer to layer applying the appropriate angles of friction. The type of the resulting earth pressure distribution can be specified in 4 different ways.
For at-rest earth pressure, the area loads are calculated by increasing by the factor k0/kah in compliance with DIN 4085 Section 6.4.3.
Alternatively, it is possible to determine the demands placed on a wall from area loads using the theory of elastic half-space. The two load concentration factors "3" and "4" can be taken into consideration (see also the following Figure).
For over consolidated, cohesive soils the concentration factor "3" applies, where:
eop = q/π · (β2 - β1 + cosβ1 · sinβ2 - cosβ2 · sinβ2)For non-cohesive soils, or for cohesive but not over consolidated soils, the concentration factor "4" applies, where:
eop = q/4 · (sin³β2 - sin³β1)
Regarding the kind of earth pressure, area loads can be defined independent of the global preferences (see menu item "Editor 1/Type of earth pressure").
It is possible to enter a horizontal load p(h) when defining area loads ("Editor 2" menu).
In this case, a horizontal load of 10 kN/m² was defined with a width of 1.50 m. This corresponds to a horizontal load H of 15 kN/m. According to the Piling Handbook (Spundwand-Handbuch) this results in the active earth pressure shown in the following figure for homogeneous ground:
The area covered by the active earth pressure resulting from horizontal loads corresponds to a horizontal load of 15 kN/m.
In homogeneous ground, the resulting earth pressure is independent of unit weight and cohesion. The earth pressure distribution with depth is acquired from the friction angle φ and from ϑ, which results from it. The earth pressure area is independent of the angle of friction and always corresponds to the adopted horizontal force H. In stratified ground the beginning and end of the earth pressure's zone of influence is acquired by averaging φ and ϑ.
If at-rest earth pressure or increased active earth pressure are adopted the horizontal forces from the resulting earth pressure cannot be greater than the acting horizontal force H for equilibrium reasons. The same earth pressure distribution is therefore adopted in GGU-RETAIN for at-rest earth pressure and increased active earth pressure as for active earth pressure.