Briefs: 1905: St Michel station the Parisian Métro
Today, freezing is widely used in tunnel construction. However, it was recent technology in 1905 when line No. 4 of the Parisian Métro system was under construction. This was the first line built under the Seine and the works proved difficult because of seepage of river water into the unstable ground through which the tunnel was to pass. How was the problem solved? By circulating brine at a temperature of -24°C through pipes in order to freeze the ground. The freezing process was applied for 40 days and the section of the Métro measuring a mere 14.5 metres took 10 months to build!