A SEMIEMPIRICAL METHOD FOR THE DESIGN OF SUPPORT SYSTEMS IN UNDERGROUND OPENINGS

A semi-empirical method has been developed for the design of support s ystems consisting of rock bolts/anchors, shotcrete/fibre-reinforced sh otcrete, steel ribs and grouted arches to support tunnels and caverns, especially in poor rock conditions. The empirical relations for mobil izing factors of shotcrete and bolts/anchors have been deduced on, the conservative side from extensive data of tire Norwegian Geotechnical Institute (NGI) tables and charts for support systems presented by Bar ton et al. (1974). There is a reasonably acceptable correlation betwee n the empirical approach and the proposed theory of estimating the sup port capacity, except for abnormal cases. The proposed method is simpl e to apply in the field. Special designs have been suggested for compl ex geological conditions for which the assumptions are not valid, such as in thick shear zones, etc.