Soil nailing

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The soil nailing serves to ensure that excavations and steep slopes , especially in irregular slope curve without shoring .

The excavation pit is excavated in sections as far as the existing soil is briefly stable. The embankment is then secured with shotcrete and ground nails, creating a force-fit connection between the nail head and the shotcrete skin. The shotcrete is applied either by means of conventional reinforcement or as fiber concrete . The thus formed composite body in situ soil then has the structural behavior of a gravity wall , whereby the effect of the steel supporting members - comparable to a reinforcement - is calculated by assuming a cohesion consideration.

Soil nailing can be used both as a temporary and permanent measure.

Definition and standardization

A distinction is made in DIN EN 1537 (replacement for DIN 4125) between anchors and nails. Nails are completely, force-fit with the ground and are not pre-tensioned. Anchors, on the other hand, have a defined grouting length and a free, non-grouted area ("free anchor length"). Anchors are preloaded. Every anchor must be checked (acceptance test), with nails pull-out tests are only carried out at a specified number per construction site.

Manufacturing

To produce a ground nail or earth nail, a hole is drilled in the intended depth (approx. 3 to 6 m) and incline in the wall to be secured. Anchor drilling rigs or drilling rigs serve as drilling rigs. Depending on the existing subsoil, the borehole is cased, drilled with auger or another method suitable for the soil. The drilling diameter mostly depends on the supporting member to be installed.

GEWI Bars are often used as support members. The borehole is completely filled with cement mortar and, if necessary, re-grouted. The connection to the shotcrete shell is made using a nail plate and a nut. These are put on after the shell has been manufactured.

literature

  • Florian Hörtkorn: Effectiveness of flexible rod-shaped elements in slope stabilization (= Geotechnik series of publications. Vol. 24). University Press, Kassel 2011, ISBN 978-3-86219-078-2 (also dissertation, University of Kassel 2009).
  • Daniel Renk: On the statics of soil nailing (= Advances in geotechnical engineering and tunneling. Vol. 17). Logos-Verlag, Berlin 2011, ISBN 978-3-8325-2947-5 (also dissertation, University of Innsbruck).