Micropiles are small diameter, drilled and grouted reinforced piles. Micropiles are non-displacement piles, usually 300 mm or less in diameter. The piles have a steel reinforcement achieved with a hi-tensile threadbar. Micropiles are designed as friction piles. EBS installs micropiles with specialized drilling equipment in sizes and configurations to match project scope and requirements.
Applications
New Construction
Micropiles are excellent for new construction in tension or compression to support a variety of structures ranging from industrial, commercial, institutional, infrastructure and residential applications from one to thirty stories high.
Retrofit
Well adapted to the challenges in retrofit applications, micropiles
are great for adding
more capacity to an existing foundation for repairs, remediation or renovation.
Tower Support
From communications to transmission towers micropiles can be installed in low headroom and remote areas with difficult access. From new installations to adding capacity to existing structures for new loads, micropiles offer flexibility and accessibility.
Slope Stabilization
In areas where traditional slope stabilization methods are not practical or feasible, micropiles offer an option that tackles access challenges and timing.
Specialty Shoring
When mobilization for large shoring equipment is an issue because of tight access, low headroom or pad requirements, micropiles can be called on to provide a solution to keep projects on track.
Advantages
Minimal Disturbance
The cased drilling operation means that surrounding soils and structures are isolated from impacts, making micropiles an excellent option in built-up areas.
Minimal Spoils
Although micropiles generate spoils and negligible vibrations during installation, the amount is significantly less than caissons reducing your project's excess soil.
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Spoil Containment
Micropile installation allows for control and containment of the minimal spoils. This is a huge advantage when dealing with contaminated soils or when minimizing mess is critical, e.g. inside a building.
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No Engineered Pad
Compared to other deep foundation systems, the equipment needed to install micropiles is lighter, takes up a smaller footprint, and does not require an engineered pad.
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Tight Access Installation
EBS installs micropiles with various equipment, from equipment capable of tracking through double-man doors to excavator-mounted options, adapting to site conditions and project load requirements.
High Groundwater Applications
High groundwater does not impact the installation or capacity of micropiles.
Install to any Depth
Micropiles can be installed to any depth from 2m to 90m to reach the suitable bearing stratum. The modular system means EBS can easily add extensions to the required depth.
Obstructions
Unlike other deep foundation options, micropiles are installed in all soil types and ground conditions. Without additional tooling or changes, micropiles drill right through site obstructions such as boulders and buried concrete.
Large Loads
When bedrock is within our considerable reach, micropiles are capable of large axial and moderate lateral loads.
EBS GEOSTRUCTURAL'S
BUILD ON Approach
At EBS, we have a passion for construction. We Live for the challenges associated with today's construction environment. Sites with poor soils, redevelopment of sites, limited access, and adjacent structures. Our team includes structural and geotechnical engineers you can work alongside to design or re-design for the most effective solution for your project.
We blend proven technologies and techniques to push projects forward, sometimes in novel combinations.
Our experienced field staff work closely with our in-house engineering team to develop solutions to site challenges.
We quickly evaluate your project and outline solutions, options, suggestions and budget pricing.
BUILD ON our Growth | Respect | Integrity | Teamwork
MICROPILE THEORY
Micropiles are not end-bearing piles. They are friction piles. Micropile capacities are based on:
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Grout-to-ground bond strength
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Mechanical strength of the reinforcing bar
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Grouting method used
Micropiles
Minimal Disturbance (adjacent structures & soil)
Minimal Vibration
Ability to work in restricted areas
Large axial loads, moderate lateral loads
Can be installed in all soil types and ground conditions
MICROPILE STEPS
Unbonded Zone / Overburden
Soil layers that do not have sufficient bearing capacity for the required loads. These layers are isolated from the micropile by the casing, which is usually left in place, and does not impact the capacity of the micropile.
Dense Bearing Strata
This dense soil layer or bedrock has sufficient depth to allow the development of the required bond length.
Casing Embedment
The casing is usually embedded 30 cm into the dense layer, ensuring isolation from the overburden. This also allows grouting of the micropile without affecting the overburden.
Bonded Zone
The required loading and the grout-to-soil/rock bond determine the bond length. (see the reference guide for examples) link to reference guide
Threadbar
The threadbar transfers the load from the structure to the bearing strata. Threadbar and couplers allow EBS to couple and terminate sections together in the field as needed without welding. With this modular system, we can adapt to site conditions like low headroom, reach the required depth, and terminate without welding.
MICROPILE DRILLING ACTION
EBS drills micropiles using a down-the-hole hammer and casing. The drill rig pushes the casing down and rotates it, isolating the drilling operation from the surrounding soil and preventing material sloughing into the hole. The down-the-hole hammer is powered by compressed air, which fires the carbide button bit, pulverizing soil and rock in the drill path. The hammering action happens at depth and high frequency, making it more efficient, requiring less power, and developing minimal vibration to surrounding soils and structures. The spoils are forced to the surface through the annular space between the hammer and casing by the high-pressure air.
MICROPILES AND OBSTRUCTIONS
A distinct advantage of micropiles is how they handle obstructions in the soil. Common obstructions like buried concrete and boulders are no problem for micropile equipment. In most cases, the tooling and techniques used to develop the micropile bond length are the same to get through obstructions. Site-specific borehole information prepares EBS for unique site conditions.
