Micropiles

Micropiles, also known as minipiles, pin piles, needle piles, and root piles, are a deep foundation element constructed using high-strength, small-diameter steel casing and/or threaded bars.

Common uses

Provide structural support to most structures

Underpin foundations

Enhance mass stability

Transfer loads

Process

The casing, with a diameter generally in the range of three to 10 inches is advanced to the design depth using a drilling technique.

Reinforcing steel, typically an all-thread bar, is inserted into the micropile casing and high-strength cement grout pumped in. The casing may extend to the full depth or end above the bond zone with the reinforcing bar extending to the full depth.

Capacities vary depending on the micropile size and subsurface profile but compressive capacities of more than 500 tons have been achieved.

Advantages

Resists compressive, uplift/tension, and lateral loads

Can be installed in restricted access and low headroom sites with minimal disruption to operations

May avoid utility re-routing

Alleviates quality assurance concerns associated with cast-in-place piling in weak soils

Can be combined with other techniques to meet unique or complex project requirements cost-effectively and efficiently