Pile Design and Construction Practice, Fifth edition

p m/c u
10.5
2p
0
and the mean horizontal pressure p m are shown in Figure 9.17. Methods of calculating p m
and the height h u are described by Springman and Bolton.
When calculating lateral forces on the piles for a range of values of c u the higher values
should be used to obtain the bending moments and pile deflections, and the lower values for
assessing the stability of the embankment. It is also important to ensure that the side slopes
of the embankment have an adequate safety factor against rotational shear failure.
De Beer and Wallays (9.29) have established an empirical method of calculating the lateral
pressure on vertical piles due to unsymmetrical surcharge loading. The surcharge is represented
by a fictitious fill of height H f with a sloping front face, as shown for three arrangements of
piles and embankment loading in Figure 9.20a to c. The height H f is given by
(9.2)
where � is the density of the fill in tonne/m3 Hf � H
.
The fictitious fill is assumed to slope at an angle � which is drawn by one of the methods
shown in Figure 9.20a to c, depending on the location of the surcharge loading in relation
to the piles. The lateral pressure on the piles is then given by
�
1.8
p z � fp (9.3)
where f is a reduction factor given by
� � 0.5��
f �
90� �0.5�� Serviceable
bearing capacity
Plastic flow around pile
h/d = 10
Pseudo-elastic
zone
(2+p)
1.5
h/d = 4
(2+p)
Elasto-plastic
zone
Local onset of yield on pile
Miscellaneous piling problems 461
Ultimate bearing
capacity
Elastic loading lines
(2+p) (1+2d/s)
Ultimate plastic failure
of soil mass and soil
around pile
Figure 9.19 Interaction diagram for horizontal soil pressure on vertical pile driven through soft clay
into an underlying stiff stratum (after Springman and Bolton (9.24) ). Crown copyright 1995.
Reproduced by permission of HM Stationery Office.
q/c u
(9.4)