NBN EN 1997-1 ANB
The NBN EN 1997-1 ANB standard determines the maximum pressure at the pile base (maximum resistance) pmax, base from the corresponding ith penetration test as follows:
where: | αp | - | |
εp | - | scale factor | |
β | - | ||
s | - | ||
qp | - | unit pile base resistance according to the De Beer method |
The Scale factor εp is determined as follows:
- for tertiary OC-clay:
- for other soil types:
where: | Db,eq | - | |
Dc | - | diameter of the CPT-cone |
The maximum shaft friction (shaft resistance) pmax, shaft is given by formula:
where: | αs, i | - | shaft friction coefficient in the ith layer |
qs,i | - | average shaft friction in the ith layer | |
n | - | number of layers along the pile |
Average shaft friction qs,i is determined as follows:
where: | qc,m,i | - | average cone resistance (qc) in the ith layer |
ηpi | - | empirical friction coefficient |
Empirical friction coefficient ηpi (or max. average shaft friction) are determined according to the soil type as follows:
Soil type | qc,m,i [MPa] | ηpi [-] or qs,i [kPa] | |
Clay | 1 to 4,5 | - | ηpi = 1/30 |
> 4,5 | qs,i = 150 | ||
Silt | 1 to 6 | ηpi = 1/60 | |
> 6 | qs,i = 100 | ||
Sandy Clay | 1 to 10 | ηpi = 1/80 | |
> 10 | qs,i = 125 | ||
Sand | 1 to 10 | ηpi = 1/90 | |
10 to 20 | qs,i = 110+4(qc,m,i - 10) | ||
> 20 | qs,i = 150 |
Literature:
RICHTLIJNEN VOOR DE TOEPASSING VAN DE EUROCODE 7 IN BELGIË VOLGENS DE NBN EN 1997-1 ANB (WTCB Rapport nr. 20 - November 2020).