Micro piles, also known as mini piles, pin piles, needle piles, and root piles, are deep foundation elements constructed using high-strength, small-diameter steel casing and/or threaded bars.
- Provide structural support to most structures
- Underpin foundations
- Enhance mass stability
- Transfer loads
The micro pile casing generally has a diameter in the range of 3 to 10 inches. Typically, the casing is advanced to the design depth using a drilling technique. Reinforcing steel, typically an all-thread bar is inserted into the 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.
This technique has been used to support most types of structures. Veda’s micro pile drill rigs allow installation in restricted access and low headroom interiors, allowing facility upgrades with minimal disruption to normal operations.
Veda can combine our micro pile technology with one or more of our other ground modification techniques to meet unique or complex project requirements cost-effectively and efficiently. Lines of micro piles spanned by wooden lagging can be ideal where excavation walls are required in low headroom and other confined areas. Post-grouting within the bond length can increase frictional forces with surrounding soils and achieve greater capacity. Micro piles can serve to “stitch” the soil together within predicted shear zones to enhance mass stability. In liquefiable profiles, micro piles can transfer loads to competent bearing strata to follow seismic design requirements.
- Resists compressive, uplift/tension, and lateral loads
- Comprehensive fleet of rigs and tooling for difficult subsurface conditions and limited access
- 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
The finished micro pile (mini pile) resists compressive, uplift/tension, and lateral loads and is typically load-tested following ASTM D 1143 (compressive), ASTM D 3689 (uplift/tension), and ASTM D 3966 (lateral). Capacities vary depending on the micro pile size and subsurface profile. Allowable compressive capacities of more than 500 tons have been achieved.