Pile Design and Construction Practice, Fifth edition

From plots of individual cone readings, shown typically for CPT 1 in Figure 4.45 the
average and characteristic cone resistances over the length of the shaft and at the base are

Resistance of piles to compressive loads 233

CPT1 CPT2 CPT3 CPT4 Average Characteristic

Shaft, average qcMN/m^2 6.0 7.5 8.4 8.5 7.6 7.35

Base, min qcMN/m^2 8.2 9.7 10.1 10.7 9.7 9.3

0

5

10

15

20

5

CPT 1

10

qc (MN/m^2 )

15

Depth below ground level

Figure 4.45

For CPT1, Shaft friction 0.008  6.0  2.87  10.5 1.45 MN
Base resistance 8.2  0.656 5.38 MN
Rcal 5.38  1.45 6.83 MN
Similarly for CPT2: Rcal 6.36  1.81 8.17 MN
CPT3: Rcal 6.63  2.02 8.65 MN
CPT4: Rcal 7.02  2.05 9.07 MN