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MICROPILES

Micropile Applications

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

Micropile Advantages
Examples of Micropiles

Advantages

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.
 
Our experience lets us quickly evaluate your project and outline solutions, options, suggestions and budget pricing.

BUILD ON our  Communication  |  Integrity  |  Growth  |  Teamwork  

MICROPILE THEORY

Image of parts of a Micropile

Micropiles are not end-bearing piles. They are friction piles.  Micropile capacities are based on:
 

  • Grout-to-ground bond strength

  • Mechanical strength of the reinforcing bar 

  • 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

illustration of 3 steps of micropile process.

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

Illustration of 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

Illustration of micropile going through 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.

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