Battling adverse conditions and difficult geology, the 7m diameter, 800m deep Sedrun II shaft in Switzerland has been completed. The shaft forms part of the 57km long Gotthard Base tunnel. Constructed by Thyssen Schachtbau, a pilot hole was bored with a Wirth raise borer through alternating hard and soft rock formations and collapsing layers. This was then reamed upwards to 1.8m in diameter. Following this, a Wirth shaft-sinker widened the hole to about 7m diameter, downwards. The average daily performance was a respectable 6m. The lining was simultaneously installed and the shaft was coated with a single coat steel-fibre shotcrete lining to 220mm thickness. Engineers at surface were also hampered by extreme weather conditions, debris avalanches and rock-falls.
