Anchor Blocks - Description.

Anchor blocks are used in situations where anchorage is required horizontally or near the ground surface or at long distances from the foundation, to keep the anchorage outside of the zone of influence of active pressures, etc. Tie beams or rods are sometimes used to transfer the load to the anchor block (see Fig. 9.42).

The anchor block gains its resistance from the surrounding ground in the form of friction, weight of earth and passive pressure (see Fig. 9.43).

The anchor block can be a wedge shape or any other suitable shape most economic for the load and surrounding ground conditions. The designer must ensure that the  friction assumed in design can be developed after construction and particular care should be taken to see that trench sides are undisturbed and that the interface is suitably constructed. In addition the movement required to generate passive resistance and friction resistance must be catered for in the design and detail to make sure that failure of other parts of the structure is not caused during the motivation of the reaction.

Fig. 9.42 Tie beam and anchor block.

Fig. 9.43 Anchor block/passive pressure.