Though included in the drilling piles category, micro-piles are particularly used to consolidate the foundations of existing structures. Their diameter varies from 6 to 35 cm. and they can be performed either vertically or sloping by perforating the foundation to be consolidated and by taking away the soils by means of drilling fluids. Then, inside the hole , a metal valve frame, usually hollow an cylindrical, is placed and set up in order to inject the water and cement grout. If necessary, the injection may be repeated  so to overflow and the hole is filled with the grout  to form a unique body with the foundations.