Pile Design and Construction Practice, Fifth edition

314 Piles to resist uplift and lateral loading
Soil cylinder of
weight W resisting
uplift by anchor plate
K u
1.0
0.8
Anchor plate
0.6
0 10 20
f
30 40 50
B
Q u
W
c
P o
H
If equation 6.5 is adapted to a pile with an enlarged base the weight of the pile is taken in
conjunction with the weight of the soil when calculating W.
It will be noted that for deeply embedded plates or pile enlargements, H does not extend
up to ground level and its value can be obtained from tests made by Meyerhof which gave
the following results:
� 20� 25� 30� 35� 40� 45� 48�
H/B 2.5 3 4 5 7 9 11
The shape factor s for deep foundations (including piles) is equal to 1�mH/B, where m
depends on the angle of shearing resistance � of the soil. Meyerhof’s values of m and the
maximum permissible values of the shape factor are as follows:
� 20� 25� 30� 35� 40� 45� 48�
m 0.05 0.1 0.15 0.25 0.35 0.50 0.60
max. s 1.12 1.30 1.60 2.25 3.45 5.50 7.60
The value of Q u calculated from equation 6.5 must not exceed the combined resistance of
the enlarged base (considered as a buried deep foundation) and the pile shaft friction. These
components are calculated as described in Chapter 4.
D
Figure 6.9 Uplift of circular plate in partly clayey (c � �) or sandy (c � 0) soil (after Meyerhof and
Adams (6.2) ).