Micropiles

A micropile is a small diameter pile, normally 3 to 6 inches in diameter, which provides a deep foundation support for various types of structures. A drill rig is used to pre-drill the micropile casing to the depth determined by a design engineer. High strength, small diameter reinforcing steel (typically, an all-thread bar) is inserted into the micropile casing, and cement grout is then pumped into the casing. A bracket is attached to the foundation wall and finished micropile, allowing us to strengthen and stabilize foundations that have settled, heaved or failed to perform as originally designed. In areas where conventional underpinning methods (i.e., helical piers and push piers) cannot be used such as hard soils or a minimum pile depth must be achieved, micropiles are a good solution. Micropiles are also an alternative to traditional concrete caissons for new construction applications in both residential and commercial projects.

Applications

Micropiles are used to transfer foundation loads from the soil near the surface to deeper, more suitable load-bearing strata. They are usually used in conjunction with various foundation attachment brackets to underpin foundations of existing structures. Micropiles can be installed in almost any type of soil and restricted access or low headroom areas. They are most often used to underpin distressed foundations, but can be used to create a deep foundation for a variety of structures.

Installation

• Holes are dug at the micropile placement points to gain access to the foundation. Typically this is done from the exterior of the building, but can also be done on the interior.
• If needed, concrete on the foundation will be chipped away to allow for the proper bracket attachment and transfer of the loads to the micropile.
• Micropiles are pre-drilled to the depth specified by the design engineer. Depth will vary based on the soils types, bearing strata and design load requirements.
• Brackets are attached to the foundation and newly installed micropile.
• Lifting, if applicable, utilizes a manifold system which helps to synchronize the lifting process. The structure will then be lifted to a maximum practical recovery.
• Holes are then re-compacted and the jobsite is cleaned up.

Advantages

• Environmentally friendly installation
• Can be used in tension and compression
• Micropiles can be used in virtually any soil type
• Minimal space requirements for installation
• Installation utilizes no impact forces and produces minimal vibration, which minimizes the risk of damage to adjacent structures
• Improved anchoring capacities and reduced settlement
• Can be designed for very large and unique loading requirements
• Most economical and reliable system when minimum pile depths are required in limited access locations