Civil Engineering Reference
In-Depth Information
Exercise 10.3
A 11 m long
×
0.5 m diameter pile is to be driven in a deep deposit of clay. The
following test results were established in a geotechnical laboratory as part of a site
investigation:
Borehole No.:
1
2
3
4
Mean undrained strength along
shaft, c
u;shaft
(kPa)
120
150
200
135
Further tests revealed that the mean undrained strength at the base of the pile can
be approximated to 1.5 times the shaft mean strength for each borehole.
The pile will carry a permanent axial load of 600 kN (includes the self-weight of
the pile) and an applied transient (variable) axial load of 250 kN.
Check the bearing resistance (GEO) limit state in accordance with Eurocode 7,
Design Approach 1 by establishing the magnitude of the over-design factor. Assume
N
c
=
9 and
α
=
0.65.
Answer
(DA1-1:
Γ
=
1.17; DA1-2:
Γ
=
1.15)
Exercise 10.4
A structure is to be supported by a series of 12 driven piles, arranged symmetrically
beneath a pile cap. Pile geometry and loading data are listed below:
P
G
=
600 kN
ξ
3
=
1.33
P
Q
=
300 kN
ξ
4
=
1.23
D
=
0.8 m
L
=
18.5 m
Ground tests results from 3 boreholes have given the following values of und-
rained shear strength:
BH 1
BH 2
BH 3
c
u,shaft
52
46
51
c
u,base
33
30
42
Assume N
c
=
9 and
α
=
0.75.
Check compliance of the bearing resistance limit state by determining the over
design factor for:
i. Design Approach 1
ii. Design Approach 2.
Answer
(DA1-1:
Γ
=
1.12; DA1-2:
Γ
=
1.10; DA2:
Γ
=
1.02)
