Pile groups under compressive loading 303The settlements in the remaining layers are calculated similarly, the results for the four
layers are tabulated as follows:
Layer Depth to centre z (m) z/B (^) z(kN/m^2 )mv(MN/m^2 ) oed(mm)
of layer (m)
1 20.00 3.5 0.16 118 0.07 57.8
2 27.00 10.5 0.47 88 0.06 37.0
3 34.00 17.5 0.79 64 0.05 22.4
4 41.00 24.5 1.10 50 0.04 14.0
Total uncorrected oedometer settlement 131.2
The above summation must be corrected by a depth factor which is given by Figure 5.23,
with and as
To obtain the consolidation settlement cthe summation is also multiplied by the geolog-
ical factor g, which is 0.5 for an overconsolidated clay. Therefore
total consolidation settlement
Total settlement of pile group due to building load only i+c 13.2 + 55.8 69.0 mm
To this figure must be added the consolidation settlement of the stiff clay due to the sand
filling. The immediate settlement is not taken into account since this will have taken place
before commencing the construction of the building.
Oedometer settle due to 4 m of sand fill for an average mvof 0.06 m^2 /MN in clay layer
Correcting for the geological factor as equation 5.24:
c 0.54.9 2.4 mm
A time-settlement calculation would show that about one-third of this settlement would
be complete before completing the pile installation. Thus
settlement of 12-storey building due to combined loading from building and sand layer
Therefore it would be reasonable to assume that the final settlement of the building would
be between 50 and 100 mm.
It will be noted that the negative skin friction on the piles was not added to the loading on
the equivalent raft when calculating the settlement of the building. However, it is necessary
to check that the individual piles will not settle excessively under the combined building
load and negative skin friction.
69.0(^23 2.4) 70.6 mm
0.069.812.1^4 1 000
1 000
4.9 mm0.850.5131.2 55.8 mmDLB 16.5/52.2522.25 0.48 LB 2.35, d 0.85.