CEN/TC 288/WG 16 - Displacement piles - Micropiles

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.

1.1   This European Standard establishes general principles for the execution of displacement piles, that means piles which are installed in the ground without excavation or removal of material from the ground except for limiting heave and/or limiting vibration as well as removal of obstructions or to assist penetration.
Piles are driven into the ground using impact, vibration, pressing, screwing or a combination of these methods.
1.2   The material of displacement piles covered by this European Standard can be:
-   steel;
-   cast iron;
-   concrete, mortar;
-   timber;
-   grout;
-   combination of above.
1.3   This European Standard covers prefabricated, cast in situ, or a combination of these methods to form displacement piles of regular shape.
Examples are given in Figure A.2 and Figure A.3.
1.4   Displacement piles may be installed in soils enhanced by ground improvement techniques. The ground improvement can be executed before, at the same time or after installation of the piles.
1.5   Other than practical considerations there are for the purpose of this European Standard no limitations regarding cross section dimensions, shaft or base enlargements, length or rake.
1.6   The provisions of this European Standard apply to:
-   single piles;
-   pile groups;
-   concrete sheet piles.
1.7   Columns constructed by ground improvement techniques (such as mixed in situ columns, jet grouting, compaction grouting, vibro flotation, stone columns) are not covered by this European Standard. Bored piles are covered in EN 1536. Steel and timber sheet pile walls are covered in EN 12063. Micropiles are covered in EN 14199.