Pile Design and Construction Practice, Fifth edition

described in Section 9.4. Floating ice on lakes and rivers can jam between piles in groups

causing them to lift when water levels rise or when the ice sheet buckles.

The most frequent situation necessitating design against lateral and uplift forces occurs

when the piles are required to restrain forces causing the sliding or overturning of struc-

tures. Lateral forces may be imposed by earth pressure (Figure 6.3a), by the wind (Figure

6.3b), by earthquakes, or by the traction of braking vehicles (Figure 6.3c). In marine struc-

tures lateral forces are caused by the impact of berthing ships (Figure 6.4), by the pull from

mooring ropes, and by the pressure of winds, currents, waves, and floating ice. A vertical

pile has a very low resistance to lateral loads and, for economy, substantial loadings are

designed to be resisted by groups of inclined or raking piles (sometimes referred to as ‘bat-

ter’piles). Thus in Figure 6.5 the horizontal force can be resolved into two components,

producing an axial compressive force in pile A and a tensile force in pile B. It is usual to

ignore the restraint offered by the pile cap; thus the magnitude of each component is

306 Piles to resist uplift and lateral loading

Dock flooded

Piles acting neutrally

Ground-water level

All piles in tension

Piles in bending

and compression

Piles in

compression

Ship under

Dock empty construction

Figure 6.1Tension/compression piles beneath floor of shipbuilding dock.

Zone

of dessicated

soil

Tree removed

Roots left to decay

Uplift on

pile in this

zone

Pile anchored

against uplift

in this zone

Compressible layer

Figure 6.2Uplift on pile due to swelling of soil after removal of mature tree.