Micropiles

Micropiles

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

Quality assurance

SAC has vast load test experience in various rock formations and the ability to design in-house based on various subsurface conditions.

HOW THEY WORK:

Micropiles transfer the structural load through unsuitable soil layers to competent foundation soils.  The loads are transferred from the foundation through the steel and grout of the micropile and shed to surrounding rock or soil via high values of friction.

WHY YOU NEED THEM:

Micropiles are generally used when there are difficult ground conditions, such as natural or man-made obstructions, sensitive ground with adjacent structures, limited access/low headroom and/or karstic geology.  They are commonly used to replace deteriorating foundation systems, for the renovation of structures, to support structures affected by adjacent construction, for seismic retrofitting or in-situ reinforcement including embankment, slope and landslide stabilization.