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Micropiles, sometimes called “minipiles” are deep foundation elements used to support load by friction between grout and the soil or rock surrounding the pile.  By definition, micropiles are generally less than 12″ in diameter and typical sizes are between 4″ and 10″.  Micropiles are installed by drilling a hole, inserting a high strength threaded bar and/or steel casing, and grouting the pile in place from the bottom up (tremie grouting).  The steel reinforcing in the micropile is usually designed to take the majority of the load applied.  Typically end bearing is ignored and the pile capacity is designed on friction along its length. 

In collapsible soils, temporary casing may be used to stabilize the hole during the drilling process.  Another installation method available for installing micropiles in collapsible soils are injection anchors, commonly called “hollow bars”.  Injection anchors use hollow steel bars and sacrificial drill bits to serve as both the drill steel while installing the pile as well as the permanent pile reinforcing.

Typical working capacities for micropiles are in the range of 50 kips to 200 kips; however, much higher capacities are possible.

Here at Axiom Foundations we have the ability to install micropiles in open, high production project sites as well as limited access areas.  We work closely with engineers, general contractors, and owners to provide the best and most cost effective micropile solution for the project requirements.

Advantages

•Micropiles can be installed in almost any ground condition.

Micropiles can be installed in very tight locations.

•In many cases, facility operations can continue with little impact.

Disadvantages

•Load can only be applied after grout curing.

•Micropiles can be more costly than other pile systems in certain cases.

•Large lateral loads can be difficult to design for.


Applications

•New foundation support

•Underpinning of existing foundations prior to adjacent excavation

•Repair of existing foundations experiencing differential settlement

•Foundation strengthening of existing cell towers, electrical transmission towers, and wind turbines

•Support of existing foundations to accommodate additional loading conditions


Project links

- Battle Creek Tower-

- U.S. National Whitewater Center-

- Blum Inc.- 

- Big Walker Tower- 

For more information on our micropile systems, get in contact with us!