Rock anchors is a high-capacity reinforcement measure used to stabilise large-scale infrastructure. In principle, they can fail in four ways: (1) rock mass uplift failure; (2) grout-rock interface failure; (3) tendon-grout interface failure; and (4) steel tendon tensile failure. Full-scale field uplift tests were performed in a limestone quarry. The tests were designed to test failure mode 1, rock mass uplift failure, aiming to estimate the uplift load-bearing capacity of the rock mass. The tests achieved a higher rock mass capacity than what was calculated with the ''weight over overlying rock cone'' method and using presumptive shear strength values along the assumed failure cone. The failure shape showed to be structurally dependent on the rock mass structure, and a uniform cone was not developed. Stress measurements showed an increase in the horizontal stress in the rock mass during the pulling of the anchor, which indicates the formation of a load arch in the rock mass. The results showed that the current design method is over conservative in a medium strong rock mass and there is a need for development in the design method for strong and unweathered rock masses.
KEYWORDS
Rock Anchor; rock mass failure; load bearing arch; failure surface; field test
