1.1 This European Standard establishes general principles for the execution of micropiles.
They are for drilled piles constructed using a drilling tool with a diameter less than 300 mm.
NOTE 1 This European Standard is not applicable to driven piles, the execution of which is governed by EN 12699.
NOTE 2 For a definition of shaft diameter see 3.3.
1.2 Micropiles are structural members to transfer actions to the ground and can contain bearing elements to transfer directly or indirectly loads and or to limit deformations. For examples of micropiles see Figure 1, Figure 2 and Figure 3. Their shaft and base resistance can be improved (mostly by grouting) and they can be constructed with (see Figure 4):
- uniform cross section (straight shaft); or
- telescopically changing shaft dimensions;
- shaft enlargements; and/or
- base enlargement.
1.3 Other than practical considerations, there are no limitations regarding, length, inclination (definition of inclination, see Figure 5), slenderness ratio or shaft and base enlargements.
1.4 The provisions of this European Standard apply to (see Figure 6):
- single micropiles;
- micropile groups;
- reticulated micropiles;
- micropile walls.
1.5 The material of micropiles covered by this European Standard can be:
- steel or other reinforcement materials;
- grout, mortar or concrete;
- a combination of above.
1.6 Micropiles can be used for:
- working under restricted access and/or headroom conditions;
- foundations of new structures (particularly in very heterogeneous soil or rock formations);
- reinforcing or strengthening of existing structures to increase the capacity to transfer load to depth with acceptable load settlement characteristics, e.g. underpinning works;
- reducing settlements and/or displacements;
- forming a retaining wall;
- reinforcing of soil to form a bearing and/or retaining structure;
- improving slope stability;
- securing against uplift;
- other applications where micropile techniques are appropriate.
1.7 Deep mixing columns according to EN 14679 are not included in this European Standard. Columns constructed by jet grouting are covered by EN 12716. Ground anchors are covered by EN 1537.