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Services > Ground Anchors

Tech9 ground anchors are the applications of Tech9 Tensioning Systems in Geotechnical Engineering.  The anchors are available for both temporary and permanent applications.  The anchors are designed to meet standard of BS 8081 and PTI recommendations for prestressed rock and soil anchors.  P.C. Strand ground anchors are normally standard products and P.C. bar ground anchors are also available upon Special Request.

Scope of Services

Tech9 provides complete ranges of services for ground anchor
systems including

  • Design and analysis of structures to determine ground anchorforces
  • Design of ground anchors
  • Supply of ground anchors components
  • Drillingof bore holes for ground anchors
  • Installatioin, grouting and testing of ground anchor systems

Typical applications of Ground Anchors

The more common application of ground anchors is for excavations where shoring is not desired due to economical or space considerations.  They may be used in conjunction with sheet piling, slurry or pile walls, prefabricated elements etc. Often these tiebacks are temporary but may also be an integral part of the final structure and designed for permanent use.  Ground anchors also permit vertical excavation close to existing structures and serve to reduce settlements to a minimum.


Definition of Prestressed ground Anchors

The basic function of ground anchors consists of transmitting tensile forces into the ground by means of:

  • The anchor head, holding the tendon under tension and transmitting the force info the structure.
  • The fixed anchor length (lv), the part of the tendon over with the force is transmitted into the ground through the bond between the prestressing steel, the grout and the soil.  It is also called the bonded length and its length is usually determined by the consultant.
  •   The free anchor length (lfr), the part over which the tendon can elastically elongate and is therefore also called the unbonded length.

Typical field testing of ground anchors

This testing is normally carried out on every ground anchor installed under a contract.  A typical test procedure would be as follows:

  • Starting from an initial jack load P0, increase load gradually to P1, where P1-P0 is roughly a third of the maximum proof load PP intended.  Note total displacement of anchor head δ11. Observe jack load readings under this constant displacement for 5 to 15 minutes depending on ground type. Release jack load gradually to P0.  Note residual displacements δ11pl of anchor head.
  • Repeat above procedure for load P2, where P2-P1 is also roughly a third of the maximum proof load.  Note anchor head displacement δ11 and δ11pl.
  • Repeat procedure for maximum proof load Pp.  Note anchor head displacements  δ11 and δ11pl.
  • If test is successful, apply load V0 to anchor.  The sketches above show a typical method employed for recording the test observations.  The test is considered successful when
  • Certain specified maximum values of plastic deformation δ11pl are not exceeded, and
  • When the effective free length of the anchor as determined from the elastic displacement is not larger than the theoretical free Anchor length lf plus half the bonded anchor length lb . In the sketches above the upper limit lu corresponds to an effective free anchor length lf + lb /2 and the lower limit line lL to an effective Free anchor length 0.9 lf.
SERVICES
Post Tensioning Works in Bridges
Ground Anchors
Stay Cable Bridges
Heavy Lifing
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