Debonding along the fixed anchor length of a ground anchorage

• Pull-out tests were carried out on a laboratory scale ground anchorage system with pre-existing debonding.
• The load carrying capacity of the anchorage decreases with increasing size of the debonding.
• The failure load for an anchorage with a rebar tendon is greater than for a smooth surfaced tendon.
• Fracture toughness of concrete/grout and steel/grout was measured over a wide range of load mix.
• Interface toughness results are consistent with the failure mechanism in the pull-out tests.

Ground anchorages are the main means of support used for safety aspects in mining and tunnelling industry. Poor installation of ground anchorages can result in partial debonding between the tendon and the grout. The effects of debonding on the load carrying capacity of a model anchorage are examined by pull out tests. The load carrying capacity is found to decrease with increasing length of pre-existing debonding at the tendon–grout interface. The fracture toughness of the tendon–grout and of the ground–grout interfaces is measured over a wide range of mixed-mode loading and the results are used to assess the likelihood of debonding at the interfaces in a ground anchorage system.