Micropiles are a deep foundation element constructed using high-strength, small-diameter (typically in the range of 100-250 mm) steel casing and/or threaded bar. As the name implies, micropile is small diameter piles constructed by the drilling process and are often keyed into rock. 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.
In a typical installation process a high-strength steel casing is drilled down to the design depth. A reinforcing bar is inserted and high-strength cement grout pumped into the casing. The casing may extend along the full length of the pile, or it may only extend along part of the length of the pile, with the reinforcing bar extending along the full length.
There are advantages of micropiles include:
- They are small and relatively light.
- They are relatively inexpensive.
- They can be installed through almost any ground condition, making them suitable for installation in environmentally-challenging conditions, such as for wind turbine towers.
- The limited vibration and noise causes little disturbance.
- Piling rigs can be low-emission or even electrically driven.
- They can be installed while avoiding existing utilities, meaning that expensive utility re-routing is not required.
- They can beinstalled close to existing walls with limited headroom and congested site conditions.
- They have a high load capacity and an ability to resist compressive, tensile and lateral loads.