Pile Design and Construction Practice, Fifth edition

Thus the load to be carried by anchorage in shale 1100 – 72 1028 kN. This load can be
resisted by an anchor cable made up from seven 15.2 mm 7-wire Dyform strands. The
breaking load of each strand is 300 kN. Therefore

which is satisfactory. The approximate overall diameter of the 7-strand cable is 45 mm.
Therefore for an allowablebond stress between steel and grout of 1.0 N/mm^2 :

Drill the cable hole to 9 m and provide an unwrapped and cleaned bond length of 7 m with
compression fittings swaged on to the lower end. The cable can be fed down a 150 mm
borehole for which,

which is satisfactory for a strong shale (Table 6.3). The stress is not excessive if the anchors
are stressed to 1.5 times the working load during installation.
From Figure 6.17a, the volume of a rock cone with a 30 half angle lifted by single anchor
cable is 0.35 93 255 m^3. The submerged weight of the rock cone 1.39.81
255/1 000 3.25 MN.

The anchorage of the whole dock floor requires 70 lines of anchors (at right-angles to the
centre-line of the dock) and 20 ranks of anchors ( parallel to the centre-line of the dock) to
form the 3 m square grid. Therefore in Figure 6.17b, N 70, M 20, and P S 3 m.
From Figure 6.17a, m/L n/L 0.57, and therefore, m n 0.57 9 5.1 m. Then
P/n s/m 0.59 so that, from Figure 6.17b,. Because
(P/n)^2 (S/m)^22 0.59^2 0.7 is less than 4, there is composite overlapping of the rock
cones, and the charts are not valid. The intersecting cones represent a rock volume roughly
estimated to be 69 3  19  3  6 70 794 m^3.
The sum giving the total force resisting uplift is thus as follows:

Weight of dock floor 237.3 MN

Submerged weight of soft clay 791.1 MN

Submerged weight of anchored rock 902.8 MN

Total 1931.2 MN

70 794  1.3  9.81

1000

210 ^60  8.0  0.8  9.81

1000

210 ^60  0.8  2.4  9.81

1000

VnVcVmVc 0.45

Factor of safety against uplift 3.25

1.03

3.1 (which is satisfactory)

working bond stress between rock and grout 1028 ^1000

 150 7.0 1000

0.31 N/mm^2

required bond length of cable 1 0281 000

 45 1.01 000

7.3 m

working load 1 028

7  300

0.49breaking load of strand

Piles to resist uplift and lateral loading 359