Grouting pile
The injection pile is inserted for structures in civil engineering and renovation pile with an outer diameter enters <300 mm (pile of small diameter), the forces of his grout into the surrounding soil or rock as tension or compression post.
"Injection piles (in-situ concrete and composite piles) with a small diameter" (previously DIN 4128 in Germany) are regulated in Europe in DIN EN 14199 "piles with small diameters (micropiles)".
Composite piles
The most important group among the injection piles are the composite piles. Earlier or other names for injection piles in the sense of composite piles were or are:
- Small injection pile
- Small bored pile
- Root post
- Anchor pile (EAU 2004)
- GEWI post
- TITAN post
- Pipe pile
- thyssenkrupp ASF drill injection pile
- ANKER-SCHROEDER drill injection pile
The bond exists between the steel support member (reinforcement) provided with reinforcing steel ribs and the enveloping grout. The transmission of forces into the ground or rock takes place via the skin friction of the grout into the ground.
Usual steel tendons are:
- GEWI steel (thread steel , solid bar), or
- TITAN steel (hollow bar)
- Round steel (with yield strengths <500 N / mm²)
- Round steel (with yield strengths> = 500 N / mm²)
Consists of ductile structural steel with rolled-on thread ribs.
Manufacturing
Composite piles are produced by installing a steel support member (the reinforcement) in a borehole, usually using a drilling process and then grouting.
Well stabilization
The borehole must be stabilized against collapse in order to ensure a free-standing annular space for later grouting. There are two common methods of hole stabilization and the installation of the steel tendon:
- Installation of temporary piping in individual sections of steel pipes (for solid rods)
- Production of a filter cake from cement suspension (for hollow rods)
Installation without drill hole stabilization is only possible in absolutely stable ground or rock.
Installation of the steel tendon
- Solid rods are preassembled and inserted into the cased borehole after drilling out the inside of the pre-casing with auger
- Hollow rods already serve as drill rods with a lost drill bit. They are drilled in directly in individual sections, hence the name “self-bored pile”.
Pressing
After the steel tendon has been installed, the annular space between the steel tendon (the reinforcement) and the soil or rock is grouted with cement mortar (water-cement mixture with or without aggregates ) and the grout is thus created. This fulfills two functions:
- Transfer of forces from the steel tendon to the ground or rock
- Corrosion protection cover
A distinction is made between:
- static crimping for solid bars and
- dynamic compression for hollow bars.
Depending on the type of soil, the type of grouting can have an impact on skin friction.
Post grouting
The post-grouting effect consists in the creation of a toothing of the grouting body with the soil and thus increases the skin friction in problematic soils. The post-grouting effect is achieved by two processes:
- Post-grouting (solid rod) via separate grouting hoses and post grouting valves, resulting in local bursting of the otherwise cylindrical grout body.
- Dynamic grouting (hollow bar), the interlocking with the ground is automatically and immediately produced over the entire length of the grouting body during installation due to the process (flushing jet of the drill bit).
Corrosion protection
The grout (cement stone) envelops the steel support member and thus acts as a corrosion protection cover. In addition, some product-specific building authority approvals require additional corrosion protection depending on the application, the steel tension used in the steel tendon, the reinforcing steel ribs used and the aggressiveness of the soil:
- Corrugated pipe (so-called "double" corrosion protection)
Further additional corrosion protection systems are:
- Hot-dip galvanizing
- DUPLEX protection
- Rust surcharge according to the recommendations of the Working Committee for Embankment Edging 2004 (EAU)
Due to different reinforcing steel ribs or thread shapes of the steel support members from different manufacturers, different corrosion protection systems can be provided for the same application in accordance with the respective building authority approvals. The name of the corrosion protection system therefore does not allow any conclusions to be drawn about its effectiveness and durability.
Applications
Areas of application are:
- Formations and post-formations
- Reinforcement of existing structures
- Underpinnings
- Reduction of settlement or displacement
- Anchoring
- Ground reinforcement
- Buoyancy safeguards
- Improvement of the stability of terrain jumps and slopes
Composite piles partially overlap in their applications with soil nails (DIN EN 14490).
literature
- DIN EN 14199: 2005-01
- DIN 4128: 1983
- DIN 1054: 2005-01
- DIN EN 14490: 2010
- SUSPA-DSI, DYWIDAG Geotechnical Systems, company publication 04170-0 / 02.06-4.000 go se
- FRIEDR. ISCHEBECK GMBH, New ways in geotechnics - design and dimensioning, company publication W 29 / 03.09 / 09.09 / 1 ISCHEBECK 2009
- General building inspection approval from DIBt No. Z-34.14-209 "Injection piles TITAN" from March 28, 2008
- General building approval from DIBt No. Z-32.1-2 "DYWIDAG GEWI Piles" from November 4, 2008
- Pfahl Symposium 2015 TU Braunschweig TK-ASF Drilled Injection Pile (Tapken / Dietz)
- Steel sheet piling "News from planning and application" Stahl Online 2015: TK-ASF drilling injection pile (Tapken / Dietz)
- Special edition ports and quays; Verlag Ernst & Sohn - March 2012: Article: Bohrpfahl (page A4 / A5) (Einkawitz / Hagemann)