Pile Design and Construction Practice, Fifth edition

The method generally used in the Netherlands is to take the average cone resistance
over a depth of up to four pile diameters below the pile toe, and the average eight pile
diameters above the toe as described by Meigh(4.25).
The ultimate base resistance is then

(4.19)

The shape of the cone-resistance diagram is studied before selecting the range of depth
below the pile to obtain. Where the qcincreases continuously to a depth of 4Dbelow
the toe, the average value of is obtained only over a depth of 0.7D. If there is a sudden
decrease in resistance between 0.7Dand 4Dthe lowest value in this range should be selected
for (Figure 4.18b). To obtain the diagram is followed in an upward direction
and the envelope is drawn only over those values which are decreasing or remain constant
at the value at the pile toe. Minor peak depressions are again ignored provided that they
do not represent clay bands; values of qchigher than 30 MN/m^2 are disregarded over the
4 D – 8 Drange.

qc 1 qc 2

qc 1

qc  1

qub

qc 1 qc 2

2

qc 2

qc 1

178 Resistance of piles to compressive loads

Cone resistance (qc) (MN/M^2 ) Cone resistance (qc) (MN/M^2 )

Soft silty clay

Loose

becoming

medium

dense

sand

Lower

bound curve

Average curve

Path for

determining qc– 1

Method used in the Netherlands

for obtaining base resistance

Depth below ground level (m)

510

0

5

10

15

20

15 5 10

Pile

D

8 D

4 D

15

0

(a) (b)

5

10

15

20

Determining qc from average

and lower bound qc /depth

curves

Path for

determining qc– 2

Figure 4.18Use of static cone penetration tests (CPT) to obtain design values of average cone
resistance ( ) in coarse soils.qc