Micropiles are a deep foundation element constructed using high-strength, small diameter steel casing and/or threaded bar. The micropile casing generally has a diameter less then 300mm Typically the casing is advanced to the design depth using a drilling technique. Reinforcing steel is inserted into the micropile casing. High-strength cement grout is then pumped into the casing. The casing may extend to the full depth or end above the bond zone with the reinforcing bar extending to the full depth. Mircopile bypass the problem soils by installing structural elements to transfer the building’s load to underlying competent soils or bedrock. This technique can be used to raise settled structures. Mircopile can be designed such that the completed solution is below-grade and the aesthetics of the structure are not compromised.

Micropiles, also called mini piles, are often used for underpinning. They are also used to create foundations for a variety of project types, including highway, bridge and transmission tower projects. They are especially useful at sites with difficult or restricted access, or with environmental sensitivity. Micropiles are made of steel with diameters of 60 to 200 mm. Installation of micropiles through top soil, sand and cobblestones overburden and into soil rock can be achieved using Air Rotary or Mud Rotary drilling, impact driving, jacking, vibrating or screwing machinery. Micropiles can also be used to construct a grout column around the shaft of a standard Helical Pile system, allowing for use in higher load applications.