When was the technique developed?

In 1848, the mines head office of Pribram (south of Prague) attempted by the use of fast setting mortar to avoid using heavy timber support in a coal mine at Wejwanow.  At the same time Karl Ritter, a Swiss engineer, proposed curved tunnel sections with immediate closure of the invert to provide a closed ring in any squeezing ground, probably as a result of the 1818 patent of Brunel's circular soft ground tunnelling shield. 

 Shotcrete was effectively invented in 1907 by Carl E Akeley, a taxidermist in Chicago where he developed a machine to spray mortar on the skeletons of dinosaurs to protect them against erosion.  The first recorded application of the shotcrete method in the tunnelling industry was in the USA in the early 1920's.

The New Austrian Tunnelling Method is often linked to a patent by professor Ladislaus von Rabcewicz, who invented the duel lining support for tunnels (initial and final linings).  This concept, however, had little to do with the application of the shotcrete but merely expressed the concept of allowing the rock to deform before the final lining is applied so that the loads are reduced. The idea behind the necessity for the deformation was based on the theoretical investigations by Engesser in 1881 and was applied by Schmid in 1926.

The original advocate of the use of shotcrete as immediate support in squeezing ground instead of more traditional heavy timber or steel support was Anton Brunner, a mining engineer from Salzburg, Austria.  The 'Shotcrete Method', as the New Austrian Tunnelling Method was known at the time, gained worldwide recognition when it was applied under the consulting guidance of Professor L Muller and Professor L von Rabcewicz in the Schwaikheim Tunnel in 1964. 

The first successful application of the method in soft ground conditions in a urban environment was in Frankfurt/Main in Germany in 1968