What Is a Micropile?
Micropiles (also called mini-piles) are a deep foundation system that relies on a series of small-diameter (5-12 inches) grouted piles to create a reliable anchor point for virtually all soil conditions. When completed, these piles generally consist of a central steel reinforcement member and hardened grout that maintains a lasting bond between the micropile and the surrounding soil.
Since loads are typically achieved through skin friction between the cement grout and surrounding soil or rock, micropiles can be built to handle high-capacity loads. Depending on whether solid bar or hollow bar micropiles are used, the micropiles can be optimized for any soil type and even anchored to shallow rock foundations, making them a cost-effective ground improvement solution in areas with Karst topography and sloping rock.
Micropile Foundations vs. Drilled Pier Foundations
Unlike a drilled shaft pier, micropiles derive a large percentage of their load capacity from the steel reinforcement bar. This reinforcement, coupled with load absorption through skin friction, makes them excellent for both tension and compression loads. Steel casing can also be added to address lateral loading requirements.
With a typical drilled pier foundation, significant cost overruns can occur due to extra rock coring. Drilled piers are extended along the face of sloping rock or when voids are encountered in the rock formation near the design bearing elevation of the drilled piers, they can collapse, and extra rock coring is required.
Micropiles reduce this risk as they extend into the rock formation and rely on cement grout to fill gaps in the soil, creating an impermeable bond between the micropile and the surrounding soil. Loads are then absorbed by the skin friction between the micropile and the soil. As a result, potential voids and gaps in the soil foundation are automatically filled during installation.
Micropile System Applications
Mini-piles can be used in a variety of applications. They are particularly useful when projects are launched in areas with limited access or weak soil. This system has become a preferred method of deep foundation stabilization for its reliability, versatility, and efficiency. It’s also an optimal solution to remediate ground stability issues beneath existing structures or buildings.
Intech Anchoring supports these products with our design expertise and fleet of rental equipment as needed. Before you can decide if they are the best option for your project, it’s vital to understand their applications.
For an overview of their components and practical uses, review this brief guide:
Micropile Deep Foundation Projects
Building a deep foundation is necessary for job sites of high capacity loads, on-site barriers, or poor soil. A micropile deep foundation project relies on groups of micropiles to deliver the exact load requirements for your application. Micropiling is a convenient option for establishing a deep foundation because they frequently do not require pre-drilling or pre-/post-grouting, streamlining installation, and reducing project costs.
Micropile Foundation Rehabilitation and Repairs
When existing foundations are compromised, micropiling installation techniques can be adapted to operate to tight confines, including in existing buildings with limited overhead space. When other ground improvement options aren’t feasible to repair the foundation of an existing structure, micropiling offers an alternative that’s just as effective and often easier to budget. Ultimately, it’s one of the more cost-effective foundation repair options, particularly when compared to foundation replacement.
Micropile Foundation Stabilization of Adjacent Structures
Micropiles can be used for projects with nearby structures or limited access. Since micropile installation equipment is smaller and less intrusive, it’s an ideal option for structures sharing adjacent walls that may interfere with the accessibility of your project.