CONDITION MONITORING & INTEGRITY ASSESSMENT OF ROCK ANCHORAGES

The Universities of Aberdeen and Bradford have been concerned with the response of rock anchorages and bolts to transient dynamic loading arising from blast operations since 1986. The main stimulus was to create a rational and safe design method for assessing how close to a tunnel face rock bolts could be installed without incurring damage due to blasting. Full scale field trials were conducted during the drilling and blasting of Penmaenbach and Pen y Clip tunnels in North Wales, where rock support was provided by post tensioned fully bonded resin bolts. At both sites the axial load and acceleration response were recorded at various distances from the blast source and at different levels of prestress. Large scale laboratory model tests were conducted to examine the behaviour of rock bolts subjected to both static and dynamic loading. In each case, the rock bolt was instrumented using electrical resistance strain gauges positioned along the fixed and free lengths. The stress distribution resulting from a range of impulse loads was investigated for different prestress levels. Finite element simulations developed from previous finite element studies (2), assisted with interpretation and generalisation of field and laboratory work. (A) For the covering abstract see IRRD 898458.