Annex A


Execution methods of micropiles

A.1 Drilled micropiles

Table A.1 — Execution methods of drilled micropiles
Drilling method Reinforcement type Filling/Grouting method Grout type Options
Rotary / flush drilling
Percussion drilling
Grab, chisel or bailer boring
Reinforcement cage Filling, concreting Grout mortar or concrete Casing
Single step grouting through temporary casing Grout or mortar  
Bearing element Filling, concreting Grout, mortar or concrete Casing
Single step grouting through:
  • temporary casing;
  • bearing element;
  • tube à manchettes.
Multi–step grouting through:
  • tubes-à-manchettes
  • special valves
  • post-grouting tubes
Grout Enlarged base
Grouting during drilling Grout Multi–stage grouting
through bearing
Permanent casing (with or without reinforcement cage) Filling or concreting Grout, mortar or concrete Enlarged base
Continuous flight auger drilling Reinforcement cage
Bearing element
Grouting/Concreting through the hollow stem of the auger Grout mortar or concrete  


A.2 Displacement micropiles

Table A.2 — Execution methods of driven micropiles
Driving method Material (casing) Cross section / Reinforcement Options / Grouting
A.2.1 Prefabricated Reinforced concrete
Steel or cast iron
Solid Shaft grouting
Open end tube Shaft grouting
Closed end tube Filling with grout ,mortar or concrete, with or without shaft grouting
Profiles Shaft grouting
A.2.2 Cast in place Temporary casing Reinforced cage Filling, concreting
Single step grouting through casing
Bearing element Filling, concreting:
Single step grouting through
  • casing;
  • bearing element;
  • tube-à-manchettes;
Multi–step grouting through:
  • tube-à-manchettes;
  • special valves;
  • post-grouting tubes;
  Permanent casing Reinforcement cage Concreting, with or without base enlargements


Annex B


Guidance on geometrical construction tolerances

The following geometrical construction tolerances should be considered for the design and execution:

  • plan location of vertical and raking micropiles (measured at the working level): ≤ 0,05 m;
  • deviation from the theoretical axis:
  • for vertical micropiles: max 2 % of the length;
  • for subvertical micropiles (n > 4): max 4 % of the length (see Figure 2);
  • for inclined micropiles (n < 4): max 6 % of the length (see Figure 2);
  • radius of curvature ≤ = 200 m depending on buckling conditions;

max angle deviation in a micropile joint = 1/150 radian.


Annex C


Minimum cover (in mm) for reinforcement and bearing element of low strength steel for cast in place micropiles taking into account exposure classes related to environmental actions as defined in EN 206–1

Exposure class Chemical aggressiveness Bearing element with grout cover Mortar Reinforced concrete
Compression Tension Compression Tension Compression and tension
XC1 – XC4 Not existing 20 30 35 40 50
XD1, XD2, XD3* Chloride, except salt water *** *** *** *** ***
XS1 – XS3 Chloride from salt water *** *** *** *** ***
XA1** Weak *** *** *** *** ***
XA2 Medium *** *** *** *** ***
XA3 Strong *** *** *** *** ***
* For XD3 special measures for the corrosion protection may be required in particular cases.
** HS cement shall be used for sulfate aggressive conditions.
*** Empty fields to be specified.



Guidance on corrosion rates

Loss of steel thichness (mm) due to corrosion for piles and sheet piles in soils, with or without groundwater (= Table 4–1 of EN 1993–5)

Required design working life 5 years 25 years 50 years 75 years 100 years
Undisturbed natural soils (sand, silt, clay, schist, …,) 0,00 0,30 0,60 0,90 1,20
Polluted natural soils and industrial grounds 0,15 0,75 1,50 2,25 3,00
Aggressive natural soils (swamp, marsh, peat, …,) 0,20 1,00 1,75 2,50 3,25
Non–compacted and non–aggressive fills (clay, schist, sand, silt, …,) 0,18 0,70 1,20 1,70 2,20
Non–compacted and aggressive fills (ashes, slag, …,) 0,50 2,00 3,25 4,50 5,75
NOTE 1 The values given are only for guidance. Local conditions should be considered and suitable values taking into account local conditions should be given in the national annex.
NOTE 2 Corrosion rates in compacted fills are lower than those in non–compacted ones, In compacted fills the figures in the table shoud be divided by two.
NOTE 3 The values given for 5 and 25 years are based on measurements, whereas the other values are extraplated.

EN 14199:2005 Execution of special geotechnical works — Micropiles