Supporting micropiles from the ground up

As urban areas continue to rapidly expand and become increasingly congested, the use of micropiles as a construction technique is becoming increasingly relevant, due to their applicability in limited space environments and their high load carrying capacity. Micropiles are ideal for projects in such areas as they require equipment with smaller footprints during installation, can support extremely heavy loads, and can be installed where there are difficult ground conditions that may not usually be appropriate for construction. To support the longevity and effectiveness of micropiles, centralizers are used to help establish even grout coverage during installation.

Achieving even grouting

Jason Linaker, Managing Director at kwik-ZIP, said that grouting the micropile once it has been installed is a key part of the installation process, and centralizers play an important role in ensuring a successful grouting process.

“Grouting needs to be correct during an installation as it plays a number of crucial roles, including transferring the imposed weight loads between the micropile and the surrounding ground; forming part of the load-bearing cross section; and protecting the micropile from corrosion by sealing it from moisture and acidic soils,” Mr Linaker said.

“Centralisers, such as kwik-ZIP’s GT series, are important as they keep the pile centered in the borehole, ensuring consistent and adequate grout cover for the length of the micropile as per relevant standards, including AS 2159-2009.

“The GT series has also been designed so that they do not impact the ability of the grout to encase the micropile due to gaps between each bow.”

Preventing micropiles from corroding

While centralizers can be used to help prevent corrosion of the pile, Mr Linaker said this is only the case if the centralizer system is not made out of metal.

“Metallic centralizers pose a risk to the overall success of a micropile installation. Micropiles are made from steel so when you put a metal centralizer on them, friction between the two can cause damage to the surface of the pile or centralizer, enabling moisture or acidic soil to come in contact and promote corrosion. When the corrosion process starts, this can then be transferred  between them, affecting the overall integrity of the installation.

“To reduce the chance of this occurring, centralizers made from inert materials should be used. A system such as the GT series are manufactured from high grade thermoplastic. This fully inert material has no moving parts and is corrosion free, increasing the chance of a successful and lasting micropile installation.”

Designed by drillers for the industry

Micropiles, especially when drilled, can also be slow and expensive to install. With projects increasingly looking for contractors who can complete installations more efficiently, it is important to have equipment that supports this.

“The GT series uses an integrated cable tie method of assembly, ensuring no additional special tools or skills are required for installation. They feature a simple locking mechanism that enables rapid installation and won’t hold up construction because of fiddly or labour intensive processes,” Mr Linaker said.

“They are also Australian designed and warehoused locally so there are no long lead times and, combined with their segmented design, allow for compact packing and thus lower freight costs.”

The GT series fit a range of bar and pipe diameters from 18mm (0.70”) OD to 65mm (2.56”) OD, and have four bow heights ranging from 10mm (0.78”) to 40mm (1.57”), so they are suitable for a wide range of ID-OD combinations.

This versatility ensures they suit a wide range of applications including rock bolts, soil nails, micropiles, anchors, and small diameter drop pipe.  They can also be used for centralising data collection tools such as downhole cameras, and geophysical logging tools, to reduce the potential for equipment damage during installation, operation and removal.