Removeable Ground Anchors using pyrotechnics – innovative, sustainable and safe-Paper

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The paper reviews removable ground anchors for temporary construction and presents a pyrotechnic method for fully extracting their steel tendons after use. Ground anchors transfer structural loads through a steel tendon and a grouted bond length. Although the grout remains underground after removal, extracting the steel can prevent interference with future construction.<br /><br />Existing options include partially removable systems, which remove only the free-length tendon, and fully removable systems using unscrewing or pull-out cones. These methods can require specialized installation, substantial pulling force, or significant time. The paper also describes a heating method for partial removal.<br /><br />The new full-removal approach places a sealed pyrotechnic device along the anchor’s bonded length during installation. When activated, controlled deflagration fractures the grout and breaks its bond with the tendon, which can then be pulled out. The authors report that the reaction does not produce a blasting shock wave and can release the tendon without damaging surrounding soil or structures. The system can be used with strands, threaded bars, or hollow bars, though strand anchors are the main focus.<br /><br />A 2024 project in Austria demonstrated the method on 27 two-strand anchors supporting an excavation beside a railway. The tendons were removed in two stages, taking nine hours in total. The paper estimates conventional removal would have required about 108 labor-hours, and reports no disruption to other construction work. Tests and site experience indicated that the anchors retained their load capacity during service and could be removed successfully after activation.<br /><br />The method may reduce removal time, excavation, site-restoration costs, and environmental disturbance. However, pyrotechnic components require careful handling, and further testing across varied ground conditions is needed to establish reliable operating guidance.

Keywords

removable ground anchors

temporary construction

steel tendon extraction

grouted bond length

pyrotechnic removal

deflagration

anchor removal method

construction excavation

Austria project

ground anchor tendon