Ground anchor
A grout anchor , also known as a pre-stressed anchor , is a built-in element that transmits an applied tensile force to a load-bearing layer in the subsoil . It consists of a steel tension member that is installed in a borehole . One end of the tension member is anchored in the subsoil by injected cement mortar , the grout; at the other end it is pre-tensioned via an anchor head that is held by the structure to be anchored. A tensile force is thus introduced into the tension member and the structure to be anchored is fixed in a certain position relative to the subsoil.
Grout anchors are used for soil and rock . In special civil engineering , for example, they are used to support construction pits at the rear and to secure floor slabs against buoyancy by the groundwater .
history
Grout anchors post-tensioned in the rock were first used in 1934 in dam construction in Algeria .
Grouting anchors for loose soils were developed at the end of the 1950s by Karlheinz Bauer , among others, for back-anchoring large and deep excavation pit walls . They were used for the first time in 1958 in Munich in an excavation pit for a Bavarian radio building. Originally, the bored pile wall of the construction pit was to be anchored with steel rods in well shafts made parallel to it . However, the company carrying out the work had problems hitting the wells. Bauer then had the anchors concreted directly in the gravel ground. With this construction method of the tie rod for anchoring components in the ground , which Bauer applied for a patent in 1958 , construction pits could be made without the previously necessary bracing with the help of tree trunks or steel struts. This eliminated the hindrance during the construction work and it became possible to create construction pit walls, anchored in one or more layers.
One of the well-known examples of use is the anchoring of the foundations of the tent roof of the Olympic Park in Munich.
features
A conventional ground anchor consists of
- the anchor head
- the tension member, usually made of prestressing steel
- the grout around the end of the tension member.
The respective force input can be controlled via a clamping and testing system. The process is now technically standardized in Germany in DIN EN 1537 and various manufacturers have general building inspectorate approval for their process. The power transmission into the subsoil takes place via the casing of the grout and is due to the bracing of the grout in the subsoil.
The construction knows
- Short-term anchors (or temporary anchors), which as a rule may be in use for a maximum of two years.
- Permanent anchors (or permanent anchors) that are used for anchoring with a service life of at least 100 years. You must therefore have appropriate corrosion protection . In addition, permanent monitoring of the force in the tension member is often necessary.
The choices include a. Strand and rod anchors .
literature
- Klaus Englert , Manfred Stocker (ed.): 40 years of special civil engineering , technical and legal developments 1953–1993 , Werner Verlag, 1993, ISBN 3-8041-1435-0
- Dimitrois Kolymbas: Geotechnics - Soil Mechanics and Foundation Engineering , Springer Verlag, 1997, ISBN 3-540-62806-1
- Helmut Ostermayer: Grouting anchor. In: Grundbau-Taschenbuch . Ed. Ulrich Smoltczyk , Ernst & Sohn, 2001, ISBN 3-433-01446-9
Individual evidence
- ↑ DIN EN 1537: Execution of special geotechnical works (special foundation engineering) - ground anchors
- ^ Walter Wittke Status and development of geotechnics in Germany , Geotechnics 1998
- ↑ German Patent Office, interpretation 1104905
Web links
- G. Dausch, KD Kluckert: Current state of anchor technology , in: Tiefbau , year 2001, issue 6, pp. 397–404
- Anker , products from ANP-Systems GmbH, accessed in 2014
- DYWIDAG Rod Anchors and DYWIDAG Strand Anchors , products of the company of the same name, accessed in 2014