Micropiles are small diameter (300mm or less) foundation elements drilled by means of small leader mounted rigs such as the Klemm KR 806 (modified) or the Hutte HBR 202. Those small diameter structural elements are drilled fully cased through the use of segmental drill pipes to desired depth. High yield stress steel rods are then inserted into the fully grouted cased hole before the segmental casings are removed.

The use of micropiles becomes an advantage in situations where the use of larger piles is not recommended, such as in soil conditions containing large boulders at depth, in areas where conventional rotary bored piles could affect the neighbouring structures or perhaps in low headroom conditions and/or karstic geology. They can also be used to augment or replace deteriorating foundation elements or for supporting slopes, embankments or general soil stabilisation.

NSCC has the experience installing micropiles of up to 25m depth, with design working loads of up to 1500kN.

Restricted Access (Low Headroom) Micropiles

Low headroom micropiles are executed by using the same technique as normal micropiles, but by deploying a very small electrically-powered drilling unit that requires very low headroom.  NSCC recently used such highly specialised drilling rigs to underpin the basement of a hotel in Dubai.

Self-Drilling Micropiles

Self-Drilling Micropiles make use of a threaded, hollow bar that is used both as a drilling tool, a grouting tool, and the micropile’s permanent reinforcement bar. The hollow bar is equipped with a sacrificial drill bit and is installed into the ground, using cementitious grout as a flushing medium.

This results in a grout body within the ground that contains a steel bar with high tensile capacity, leading to micropile capacities of 1,500 kN. This method is effective in unstable ground conditions and, due to its installation methodology, it is the fastest and most efficient micropile installation method.