Micro pile
Small-diameter bored piles for retrofitting foundations, building works on existing properties and confined spaces

Micro-piles are small-diameter driven piles used for a variety of foundation and stabilisation applications. They are particularly suitable for retrofitting foundations, reinforcing structures, as well as for projects where space or working height is limited.

Encyclopedia: Micro pile

In accordance with DIN EN 14199
Micro piles for foundations and anchoring

Micro piles are used as foundation and anchoring elements in soil and rock. The permissible pile loads and member lengths are designed individually for each construction project on the basis of the geological and project-specific boundary conditions.

Various drilling methods are available for their installation, which are selected according to the respective subsoil and site conditions. The various design variants allow for adaptation to different project requirements and operating conditions.

Using our own drilling equipment, boreholes can be drilled even in confined spaces, at limited working heights or at great heights. Micro piles are also referred to as small-diameter drilled-in-place piles, micro-drilled piles or composite piles.

1:26 Minute

Animation – Micro pile

04:07 minutes

Explanatory video – The micro pile

Technical brochure
Micro pile

Technische Broschuere Mikropfaehle und Naegel

Micro piles (only available in German)

PDF

Applications

Micropiles are used as precisely fitting foundation and anchoring elements.

Common uses include:

Deep foundations
Replacing the foundations of existing buildings
Bracing
Anti-buoyancy control
Embankment reinforcements
Anchoring

Benefits / Features

Adaptability: Can be adapted to different ground conditions.
Load-bearing capacity: Designed to accommodate different pile loads in accordance with project requirements.
Construction: Low-noise construction with minimal vibrations is possible.
Operating conditions: Construction is possible even where working height is limited, thanks to the modular design.
Method: Application based on general type approvals from the German Institute for Building Technology (DIBt).
Quality assurance: Execution in accordance with defined quality and monitoring measures.
Execution: Use of the flushed drilling method with varying daily output depending on subsoil conditions and project requirements.
Scope of application: Can also be used in construction projects where the absence of unexploded ordnance has not been confirmed; the relevant permit under Section 7 of the Explosives Act (SprengG) has been obtained.
Production: Micro piles are manufactured in our own factory.

Basic facts

Standards and regulations

Micropiles are dimensioned in accordance with:

DIN EN 1997-1: Eurocode 7
Recommendations of the DGGT “Piles” working group (EA-Pfähle)

The following apply to the production of micropiles on the construction site:

DIN EN 14199 Execution of work in specialist civil engineering – Micropiles
DIN SPEC 18539 Supplementary specifications to DIN EN 14199

Micropile testing is performed in accordance with:

DIN EN 1997-1: Eurocode 7
Recommendations of the DGGT “Piles” working group (EA-Pfähle)

Further details are defined in the DIBt general type approvals.

How do micropiles work?

Micropiles transfer an applied force (pressure and/or tension) via skin friction into a load-bearing layer of the subsoil. They consist of a continuous load-bearing element, which can also be formed from segment pieces that have been coupled together. The load-bearing element is encased in cement blocks along its entire length. Additional injections can be applied to suitable soil types in order to increase the load-bearing capacity.

Rods with rolled-on or rolled-up threads can be used as load-bearing elements. Another alternative is to use load-bearing elements that also serve as drill rods. Reinforced in-situ concrete piles with a pile diameter of up to 300mm are also referred to as micropiles or micro bored piles.

Anti-corrosion protection is provided by the cement block coating with crack width restriction or by means of factory-made extruded coating made from PE piping.

Dimensioning

Dimensioning micropiles involves defining both the length of the micropile and the necessary pile force. An estimate is also made of the length of the force application section. Lower pile forces can be applied in cohesive soil types such as clay and silt than in non-cohesive soil types such as gravel/sand or rock.

Manufacturing stages

Each stage has a particular significance for the load-bearing capacity and durability of a micropile.

1. Drilling and replacing the drilling water

The drilling method used can have a strong influence on the load-bearing capacity of a micropile. This is why it is important to choose the right drilling method. Our many years of experience have equipped us to work with a wide variety of soil types, so that we can always use the best possible method.

2. Installing and grouting the load-bearing element

Care must be taken during storage, transport and installation of the load-bearing element in the borehole to ensure that the protective anti-corrosion casing is not damaged. Our construction teams are specially trained in these processes.

After the pile has been installed in the slurry-filled borehole, the shaft of the pile is formed by applying grouting pressure. It is important to choose the right type of cement and the correct amount of grouting pressure. Targeted follow-up injections, which can be carried out several times, if necessary, can significantly increase the load-bearing capacity in non-cohesive soil types.

3. Load test

Some of the micropiles must be tested under trial loads. The specifications of the type approvals and the relevant provisions must be observed. Where tension micropiles are used for anchoring breaks in the terrain, it is important to bear in mind that the piles undergoing testing must be produced so that the load is applied to the load transmission section that has been defined for the final state. This means that additional measures must be taken to exclude skin friction above the load transmission section in the test piles.

4. Installing the pile head

The final stage of producing a pile is installing the pile head. A range of different variants are available here. An anchor plate with a counter plate is generally used.

Quality assurance

We ensure high execution quality with:

Individually coordinated instructions
Our own DIBt general type approval for micropiles
Compliance with the requirements of execution standard DIN EN 14199
In-house production of the micropiles in Germany
In-house and third-party production monitoring
Clear processes governed by our quality management system in accordance with DIN EN 9001:2015
Professional pile test loading in accordance with DIN EN 1997-1 and DIN EN 14199

Auf dem Bild sieht man eine Maschine des Spezialtiefbaus ,beim Einbau von Mikropfählen, die von einem Panton aus an einer Hafenmauer arbeitet. Davor steht ein Mann mit Helm der die Arbeit überwacht. Er erstellt einen Mikropfahl. — Rückverankerung mit Bohrverpresspfählen, Duisburg Werkshafen HKM

© PORR

Design variants

Micro piles are available in a range of designs for various foundation, stabilisation and anchoring applications. Depending on the subsoil conditions and project requirements, different systems, corrosion protection options and anchoring techniques can be employed.

These include piles with: buoyancy control systems – protection against buoyancy forces

compressive, tensile or alternating loads
permanent or temporary use
single (SKS) or double (DKS) corrosion protection
steel buckling protection sleeve or PE pipe for force decoupling
plate anchoring or adhesive anchoring

Micro piles are used to secure structures against buoyancy forces. Areas of application include, amongst others, structures with basements, hydraulic engineering structures or water management facilities.

Depending on project requirements, micro piles can be combined with structural concrete, jet-grouted bases or other foundation elements. The design takes into account the structural, geotechnical and project-specific constraints.

Renovation of existing buildings – retrofitting foundations in existing structures

Micro piles are used as foundation and renovation elements in existing structures. Areas of application include, for example, changes in the groundwater level or structural modifications to existing buildings.

Thanks to a variety of equipment and system options, installation is possible even where working height is limited. The choice of design is made taking into account the respective project and site conditions.

Retro-anchoring – Anchoring systems for structures and changes in ground level

Micro piles can be used as anchoring elements for changes in ground level, foundations, underpinning works and abutments.

Depending on the subsoil conditions and project requirements, different micro pile systems and grouting techniques are employed. The design is carried out in accordance with the structural and geotechnical requirements of the respective project.

Flush drilling – drilling methods for varying subsoil conditions

In flush drilling, cuttings are removed via an external flushing system. The method is adapted to the specific subsoil and project conditions.

A range of equipment and site facilities are available for carrying out the work. The choice of drilling technique is made taking into account the technical and project-specific requirements.

Pressure-sensitive drilling – drilling method for sites where explosive ordnance is suspected

For projects in areas where the absence of explosive ordnance has not been confirmed, pressure-sensitive drilling methods are available.

The work is carried out under the supervision of suitably qualified experts and in accordance with the applicable legal requirements. PORR special civil engineering holds the necessary permits for these services in accordance with the Explosives Act.