Civil Engineering Reference
In-Depth Information
2.
Design Approach 1, Combination 2:
Design resistance: partial factor set R4 is used (Table
10.3B)
:
R
R
212
2 0
740
1 6
b k
;
s k
;
R
=
+
=
+
=
568 5
.
kN
c d
;
γ
γ
.
.
b
s
Design actions: partial factor set A2 is used (Table
5.1)
:
F
500 1 0 150 1 3
.
.
695
kN
=
×
+
×
=
c d
;
568 5
695
.
Over-design factor,
0 82
.
Γ =
=
Since
Γ
<
1, the design of the pile does not satisfy the GEO limit state requirement.
10.6.4 Ultimate compressive resistance from dynamic tests results
Although static load tests and ground tests are the most common methods of determining the compres-
sive resistance of the pile, the resistance can also be estimated from dynamic tests provided that the test
procedure has been calibrated against static load tests.
10.7 Pile groups
10.7.1 Action of pile groups
Piles are usually driven in groups and connected at the top to a pile-cap onto which the structural load
is placed (Fig.
10.10)
. The zone of soil or rock which is stressed by the entire group extends to a much
greater width and depth than the zone beneath a single pile.
Failure of the group may occur either by failure of an individual pile or by failure of the overall mass of
soil supporting the group.
i.
End-bearing piles
In the case of end bearing piles the pressure bulbs of the individual piles will overlap if the spacing
between the piles is less than 5 times the diameter of a single pile. This is the usual condition. Provided
L
diameter, d
B
D
Pile group
(plan)
Single pile
Pile group
Fig. 10.10
Pile group arrangement.
