Shaft Bearing Capacity
The vertical bearing capacity of the shaft is given by the formula:
where: | Rs | - | shaft resistance |
As | - | contact area (only on the side facing the foundation pit) | |
qs | - | skin friction |
The contact area is important for the shaft bearing capacity, where the friction between the shoring structure and the soil is considered. For standard rectangular and pile walls, this area is automatically calculated by the program. For other cross-sections (sheet piles, steel profiles, user input) it is necessary to enter the coefficient of the contact area KCA, by which the user determines the contact area corresponding to one running meter of the structure.
where: | KCA | - | coefficient of the contact area |
t | - | depth of the structure below the bottom of the pit | |
b | - | structure width (1 running meter) |
For sheet piles, the KCA coefficient is normally considered as the length of the sheet piles (sum of the green sections L1-L5 in the figure below) in one running meter of the structure.
For steel sections, the KCA coefficient is usually considered as the sum of the perimeter of the sections (sum of the green sections in the figure below) in one running meter of the structure.
Determination of skin friction qs should be part of the geological survey.
Recommended values of peak resistance qs [kPa] can be found in professional literature, e.g. in the EA-Pfähle book.