Abstract
The support of engineering structures such as tunnels, retaining walls, mines, dry docks, dams and pre-stressed structures commonly involves the installation of ground anchorages. Safety is a critical issue for these structures especially for the tunneling and mining industries. Much attention is therefore focused on the integrity of roofs of mining tunnels. One approach is to stabilize the roof with grout or resin anchors. Current testing methods for such anchors are expensive and time consuming. This paper reports the results obtained from integrity testing of rock anchors from low impact blow by analyzing the frequency response curves obtained from acceleration-time trace using the principles of stress-wave propagation theory in steel bars. Laboratory experiments were performed on bolt-grout systems with varying lengths and having predefined defects. An analysis method to determine the free and embedded length of anchor bars in grout is proposed based on the results and experience obtained.