Pile Foundations - Elements of Soil Mechanics - page 310

The pile will carry a permanent axial load of 500 kN (includes the self-weight of the pile)
and an applied transient (variable) axial load of 150 kN.
Check the bearing resistance (GEO) limit state in accordance with Eurocode 7, Design
Approach 1 (UK) by establishing the magnitude of the over-design factor. Assume N c = 9
and α = 0.7 and assume explicit SLS verification has been undertaken.

Solution:

2

0 7
4

2

π D π × .

Area of base of pile A , = = = 0 385 . m

2

b

4

The total resistance is determined from the results from each borehole:

( R ) = ( N c A × × ) + × × × × ( π D L α c )

b cal ; 1 c u b u

= × × ( 9 90 0 385 . ) + × × × ( π 0 7 10 0 . . 7 65 × ) = 1312 kN

( R ) = × × ( 9 79 0 385 . ) + × × × × ( π 0 7 10 0 7 62 . . ) = 1228 kN

b cal 2 ;

( R ) = × × ( 9 96 0 385 . ) + × × × × ( π 0 7 10 0 7 70 . . ) = 1410 kN b cal 3 ;

( R ) = × ( 9 100 0 385 × . ) + × × × × ( π 0 7 10 0 7 73 . . ) = 1470 kN

b cal 4 ;

1312 1228 1410 1470
4

+ + +

( R

c cal mean =

) = 1355 kN

;

( R ) = 1228 kN i e Borehole ( . . 2 )

c cal ; min

From Table 10.4B, ξ 3 = 1.38; ξ 4 = 1.29.

( R ) 1355

1 38

c cal ; mean

R = = = 982 kN

c k ;

.

ξ 3

( R ) 1228

1 29

c cal ; min

R 952 kN

= = = c k ;

ξ 4 .

that is, (R c;cal ) min governs and this lower value of R c;k is taken as the characteristic com-
pressive resistance.
Therefore, using ξ 4 :

9 79 0 385
1 29

× × .

Characteristic base resistance , R b k = = 212 kN ,

.

π 0 7 10 0 7 62
1 29

× × × × . .

Characteristic shaft resistance, R s k = = 740 kN ,

.

1. Design Approach 1, Combination 1:
Design resistance: partial factor set R1 is used (Table 10.3B ):

R R 212

1 0

740
1 0

b k ; s k ;

R = + = + = 952 kN c d ;

γ γ . . b s

Design actions: partial factor set A1 is used (Table 5.1) :

F = 500 1 35 150 1 5 × . + × . = 900 kN

c d ;

952
900

Over-design factor, Γ = = 1 06 .