Inner ring road connecting Prague 6 to Prague 7 through Mrasovka Hill and on south to Bohemia. 1.2 km-long western tube under construction from both ends using NATM techniques in Prague black shale. Metrostav is advancing from the Severni portal using excavators on a three-compartment top heading following a crown pilot drive, while Subterra is developing cautiously past numerous obstacles in harder rock from the less-accessible Jizni portal using an Atlas Copco L2C drillrig. Both are using L2C drillrigs for rockbolting and erecting lattice girders with mesh and shotcrete. Extensive use of Swellex bolts. More details from www.okruhsmichov.cz December 1999.
