7 Design considerations
This clause deals with those matters which should be taken into account in the execution stage of a ground anchor so that the design of the anchor system may be fulfilled.
For the detailed design of a ground anchor reference should be made to annex D of this standard. For the design of the structure as a whole reference should be made to ENV 1991-1-1: Eurocode 1 Part 1-1 and ENV 1997-1: Eurocode 7- Part 1.
Anchored structures can consist of the following types of structures:
- retaining structures;
- embankment and slope stabilizing structures;
- underground openings;
- underground structures and basements subjected to uplift forces due to ground water;
- structures transferring tensile loads generated by the superstructure or by actions on the superstructure, to the ground.
The following should be clearly shown on construction drawings, where appropriate:
- minimum cross-sectional dimensions and material characteristics of all elements within the anchor system;
- dimensions of fixed and free anchor lengths;
- angle of inclination of boreholes to accommodate the anchors;
- tolerances on anchor dimensions, inclinations and anchor locations.
The design of the anchor system is based on soil parameters and the geometry of the anchor arrangement. Where changes in the anchor locations, spacings or inclinations are proposed, appropriate studies or proving tests should be undertaken to demonstrate the suitability of such an arrangement.
The design of the anchor should address the following:
- loads and constraints of loading imposed by the anchors on the overall structure as an assistance to the overall structural designer;
- the way in which the loads will be applied to the anchor during its design life i.e. static or dynamic;
- the load distribution of the anchor arrangement on the structure during stressing and during the design life of the structure;
- the interface between the anchor and the structure to ensure structural stability at all times;
- the consequence of anchor failure during stressing and thereafter, and the possibility of the allocation of reserve locations for replacement anchors, if required.