Pile Design and Construction Practice, Fifth edition

Figure 9.1Use of piles in underpinning (a) Remedial measures to support column base
(b) Precautionary measures in underpinning strip foundation adjacent to deep excavation
(c) Jacked piles to strengthen column base (d) Drilled piles to replace existing piles beneath
raft slab.

Column base

to be underpinned

Steel plates and

dry packed mortar

Concrete

surround

Existing load-bearing

wall

Bored-

and-cast-

in-situ

piles

Needle beams

Soft clay

Column propped

at higher level

Packing

plates

Steel

block

Bearing

plate

Piled

jacked

down to

bearing

stratum

Hydraulic

jack in

inverted

position

Timbering

to pit

Slab raft

Pad foundation

Timber

sheeting

secured to

the face of

piles

Limiting line beyond

which settlement of

ground due to basement

excavation will not

cause excessive

settlement of shallow

foundations

Steel H-piles

Holes drilled

in raft

Existing piles

(deteriorated)

New underpinning

piles

Spreader beams

Bearers

(a) (b)

(c)

(d)