foundation system of burj al arab

Micropile 101

Cracks and settlement are facts of life when it comes to construction using concrete foundations. There have been many methods of repairing structures once they have settled, including helical piles, push piers and Micropiles. Each has it’s own uniqueness and applications where they should or should not be used. Helical piles are a simple and cost effective solutions to light weight structural repairs. Push piers are great for lifting heavy structures in a cost effective manner. Now, Micropiles are growing in popularity for reducing the effects of settlement in new and existing structures.

There are many names for Micropiles – minipiles, pin piles and root piles being the most common. These piles are rotary drilled and grout reinforced small diameter piles which can be installed to depths of 200 feet and through very dense layers of soil and rock. Unlike helical piles or push piers, Micropiles are unaffected by cobbles and trash in the soil. Their sacrificial bit is designed to drill through these tough soils and embed themselves in load bearing rock layers, while maintaining a grout column around a structural steel member in the center of the column.

Like helical piles and push piers, Micropiles can be installed in limited access areas with relatively small equipment. This maneuverability makes them ideally suited for foundation repair applications. Portable equipment has been developed to allow for access to basements and other low overhead applications where soils or access is limiting to other more conventional methods of foundation repair.

The process of installing Micropiles begins with drilling into bedrock using a specialized drilling rig. Soil cuttings are expelled with air, water or grout followed by grouting the column that has been created by the sacrificial carbide bit and threaded rod. The Micropile tops are cut to elevation and a sleeve is inserted to adapt to the underpinning bracket system. Load testing can be easily performed on production piles or test piles near the proposed locations.

Micropiles and their inherent advantages have grown in popularity and acceptance by contractors and engineers alike over the past several years. With the advancements in drilling equipment and underpinning brackets, Micropiles are sure to become more popular in the foundation repair industry.

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