ABSTRACT
Rock bolts were used for pressuport and to provide early support near the heading during excavation of large underground station chambers in metaraorphic rocks, locally very blocky and seamy. The bolts were useful to decrease the rate of loosening and reduce the potencial for rock falls. Rock bolts and a thin shotcrete lining alone could not provide complete stability of the 18 to 24-m-wide openings and a permanent shotcrete steel rib support was installed shortly behind the excavation face. Timely placed rock bolts of adequate length and capacity, combined with shotcrete, provided the permanent support of some vertical sidewalls. A substantial rock bolt and shotcrete support system was required to provide adequate support of multiple drifts in very blocky and seamy rock.
