Pile Design and Construction Practice, Fifth edition

286 Pile groups under compressive loading

Measurements of the relative loads carried by the piles and the underside of the slab of a
piled basement raft were described by Hooper(5.35). The measurements were made during
and subsequently to the construction of the 31-storey building of the Hyde Park Cavalry
Barracks in London. The 90 m high building was constructed on the piled raft 8.8 m below
ground level. The 51 bored and cast-in-place piles supporting the raft had a shaft diameter
of 910 mm and an enlarged base 2400 mm in diameter (Figure 5.41a). The piles were
installed by drilling from ground level and concreting the shaft up to raft level before
commencing the bulk excavation.

17.2 m OD

19.2 m OD

9.4 m OD

Mv in m^2 /MN

0.1 0.2 0.3

 10

15.5 m OD

 20

 30

0

OD

level in m

25.6 m

2 440 mm bases

23.5 m

1.4 m

300

250

200

150

100

50

0

5

10

15

20

25

Settlement in mm

Building weight in MN

Ground floor

3rd floor

28th floor

Buildingcomplete

Ws  WP

Calculated total

building weight

Measured weight Ws carried by soil

at underside of raft

20 30 40 50 60 70

Time in months

Settlement at centre of raft

Gravel  10

910 mm

bored

piles

London

Clay

10

Measured weight WP carried by piles

Buildingoccupied

(a)

(b)

Average

value

Figure 5.41Piled raft foundations for Hyde Park Cavalry Barracks, London (a) Foundation arrangements
and soil characteristics (b) Distribution of loading between raft and piles.