Excavating shield with a cutter

On 15 June 1985 the basic assembly was completed and comprehensive functional tests were started. Less than a month later, the actual excavation began, during which the forward shield was supplemented by a hanger containing, for instance, a transformer platform and a lute pull assembly platform. The first 6 metres of the tunnel were reinforced with cast iron segments and the next part with a reinforced concrete lining according to the design.

In October 1985, excavation continued in the form of comprehensive functional tests under load with simultaneous training of the crews. It is recorded that a total of 94 changes and additions were made to the shield complex during the trial operation.

What did the first Czechoslovak tunnelling shield actually look like? It was a shield with a cutter, which is why it came to be called RŠF-1. The SčN-1S body was used as the shield, from which the inner bulkheads were removed and replaced by a massive lower bulkhead serving as a support bridge for the cutter, lining stacker, and work platform. A sealing ring was inserted at the rear of the shield to both support the push rollers and spread their force effects on the lining to seal the intermediate rings during the filling grouting. The rubble was carried out of the shield by a rack conveyor onto a conveyor belt, which was further conveyed to the filling station into monorail carriages. In addition to other technologies, the hanger was equipped with a conveyor groove to move the lining components to the paver.

The RŠF-1 shield achieved an average monthly distance of 79.92 m on the excavated sections of Line B, with a monthly peak of 164 m, the highest-ever performance. Other shields of Czechoslovak origin were also being developed. The plan was to build the RŠF-2 shield, which, according to the plans of the time, was to be "supplemented with other new ideas so that it would be built to achieve an average monthly output of 120-140 m, with a maximum of 200 m ". However, it was never produced. Our country in the heart of Europe went through a change of political system and, in short succession, a breakup, and from the mid-1990s onwards the New Austrian Tunnelling Method (NATM) found its place in the limelight.