The basic concept of piling works, is to transfer the loads of the construction through upper weak soil layers to more competent deeper soil layers
   
Due to the small diameter of micro-piles, they can only sustain the loads applied to them by the skin friction interaction between their surface area and the surrounding soil layers.
   
To improve such friction interaction, skin grouting is performed around the pile shaft at the depth of penetration of the pile through the bearing strata.
   
The soil adjacent to / surrounding the pile shaft is grouted by cement mortar to cover a pre-determined length by using tube-a-manchette method, or though grouting pipes attached to the reinforcement cage of the micropile as in Post Grouted Bored Piles.
 
 

Further interesting information