Check/Design:
- Check: Calculation based on 1 drive level "Pile foot level";
- Design: Capacity calculation with drive level based on step value "zone interval" between "start zone" until "end zone".
Single pile/Pile group:
- Single pile [Reference: Negative skin friction calculation based on NEN-EN1997-1#7.6.3.3 (8b)];
- Pile group [Reference: Negative skin friction calculation based on NEN-EN1997-1#7.6.3.3 (8c) & (8d)].
The footplate thickness tp of the steel tube pile (Fig. 1) is ignored, because it doesn't have any significant influence in to the calculation:

Fig. 1. Tube pile with the closed tube base