The mean and minimum values of RcalareRcal(mean) (6.82 8.17 8.65 9.07)/4 8.18 MN
Rcal(min) 6.82 for CPT1The above values are divided by the correlation factors 1.31 (mean) and 1.20 (min) for
four cone tests (Table 4.6) to give the characteristic values:
Rck(mean) 8.18/1.31 6.24 MN
Rck(min) 6.82/1.20 5.68 MNThe design value Rcdwill be calculated from the minimum Rckof 5.68 MN. A ‘stiffness
factor’will not be applied.
Using design approach DA1 combination 1 (sets A1 M1 R1) for a driven pile in
compression the factors band sfor M1 and R1 sets are unity (Tables 4.2 and 4.5).
Therefore, Rcd 5.68 MN which is greater than the design action for A1 of 4.44 MN.
For DA1 and combination 2 (sets A2 M2 R1) band sare 1.25 (the value for )
and R4 is 1.3. Therefore design Rcd 5.68 / 1.25 1.3 3.49 MN, which is greater than
the design action for A2 of 3.29 MN.
The above calculations show that the allowable load of 3.29 MN as calculated by
permissible stress methods complies with the recommendations of EC7.
The ultimate resistance of the open end pile can be calculated by the ICP method.
Assuming that the sand has a D 50 size of 0.03 mm, Figure 4.21 gives a value of 27 for the
interface angle of friction, (^) cv. From equation 4.24, the equivalent radius of the open-end pile is
R* (0.457^2 0.438^2 )0.5 0.130 m
The shear modulus G in equation 4.31 can be calculated from Figure 5.24 and equation 6.49.
Figure 5.24 gives E 50 30 MN/m^2. Take Poisson’s ratio as 0.2, giving G 30/2(1 0.2)
12.5 MN/m^2
Take the average roughness as 2 1 10 –^5 mm. From equation 4.30:
2 12.5 2 10 –^5 /0.457 0.001 MN/m^2
This is small in relation to as calculated below and can be neglected.
The 10.5 m of embedment into the sand is divided into 9 1.0 m segments and an upper-
most segment of 1.5 m (the limiting height to the lowermost segment of 8.0 0.13 m 1.04 m
is not exceeded).
Calculating for the lowermost layer, the effective overburden pressure at the centre of
the layer is (8 6.50 10 10.0) 152 kN/m^2 , and the average qcis 9.5 MN/m^2. Take
Pa 100 kN/m^2. From equation 4.29, 0.029 9.5 (152/100)0.13 (0.5/0.13)0.38
0.174 MN/m^2. From equation 4.27:
Unit shaft resistance 0.174 tan 27 0.087 MN/m^2
Shaft resistance on segment 0.087 2.87 0.250 MN
The resistance of the remaining segments to the top of the sand layer is calculated in the
same way as shown in the following table.
rc
rc
rc
rd
234 Resistance of piles to compressive loads