Micropiles Systems and Setup

Foundation Support Systems

Micropile and minipile systems are preferred methods for supporting new construction of buildings, bridges, highways, towers, and other man-made structures. These systems are also used for underpinning and stabilizing existing structures. They are designed by geotechnical engineers and constructed with conventional materials.

Heavily loaded…karst pinnacled Though often used interchangeably, the terms micropile or minipile are not synonymous. The terms depict the diameter of the steel casing used, i.e., micropiles use casing 2 – 5 inches in diameter while minipiles use casing 6 – 12 inches in diameter. To install either, casing is drilled vertically or near-vertically through soil and into competent rock. The casing and the annulus (the space between the casing and the wall of the drilled hole) are filled with slurry grout – from the bottom-up, to flush out any debris. After curing, this creates a steel and concrete column that is effectively glued into the competent rock socket and into the entire length of the drilled hole. Micropiles and minipiles are frequently reinforced with threaded bar that is inserted into the pile to increase the load capacity. They can penetrate to depths of greater than one hundred feet and support hundreds of tons.

Support piles (both mini and micro) are preferred to driven piles when they will be very heavily loaded, when the underlying rock is pinnacled, or when overhead obstacles are a problem. (When headroom is restricted, micro/minipiles can be built in close quarters by coupling short lengths of drill rod and casing.) Rembco often uses micropiles and minipiles as an economical alternative to large diameter drilled shaft systems, especially in difficult ground conditions, karst geology, or restricted access situations.

Micropiles – Minipiles – Setup Sequence

Drilled in bedrock and bonded to the rock socket for load transfer to the wall.

  • Advance casing through earth and rock – into bedrock (competent rock)
  • Remove drill rod, leaving the casing in the hole and resting at the bottom of the rock socket
  • Pump grout into the hole, filling it from the bottom-up to fill both the annulus and the casing
  • Cut-off pile tops to the desired elevation and then cap them with a steel plates to attach to the foundation
  • Load test some or all piles to prove the system meets performance specifications
Video: Micropiles Overview
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