Pile Design and Construction Practice, Fifth edition

the soft clay),  1 0.75 and  0 0.92. Therefore

immediate settlement

From Figure 5.13 the average vertical stress at the centre of a layer of thickness 2B is
0.3 194 58 kN/m^2.
The depth factor dfor is 0.81 and the geological factor gis 0.5.
Therefore, from equations 5.23 and 5.24

Part of the imposed loading will not be sustained and will not contribute to the long-term
settlement. Thus the total settlement under the vertical load of 30 000 kN will probably
not exceed 30 mm. It is necessary to estimate the amount of tilting which would occur
under sustained wind pressure, i.e. the immediate settlement induced by the horizontal wind
force of 1500 kN producing a pressure under the combined vertical and horizontal
loading of on the equivalent raft caused by the eccentric
loading. For L/B 13/5.54 2.3, H/Band D/B 7.7/5.54 1.4,  1 1.0 and  0 0.9
giving

immediate settlement

Of this amount 16 mm is due to vertical loading only, giving a tilt of 10 mm due to wind
loading. A movement of this order would have a negligible effect on the stability of the tower.
The horizontal force on each pile if no wind load is carried by the pile cap is
1500/22 68 kN. A pile 1 metre in diameter can carry this load without excessive deflection
(see Example 6.4).

Example 6.8

Pressuremeter tests made at intervals of depth in a highly weathered weak broken siltstone
gave the following parameters:

Pressuremeter modulus Em 30 MN/m^2

Limit pressure pl 1.8 MN/m^2

Creep pressure pf 0.8 MN/m^2

The above values were reasonably constant with depth. Draw the deflection curve for a
horizontal load applied to the head of a 750 mm pile at the ground surface up to the ultimate
load, and obtain the deflection for a horizontal load of half the ultimate.

Moment of inertia of uncracked pile ^  0.75

4

64

0.0155 m^4

1.0  0.9  416  5.54  1000

80  1000

26 mm

30 000/(135.54) 416 kN/m^2

c 0.5  0.81  0.05 ^58 ^2  11.2 ^1 000

1000

26 mm

D/LB 0.62

0.75  0.92  194  11.2  1000

80  1000

19 mm

372 Piles to resist uplift and lateral loading