The construction of the third ring road highway in Moscow meant that a new road tunnel had to be constructed to pass under the Moscow to Riga railway line. Rail traffic was not to be disrupted on any account during construction. The pipe arch method of tunnelling was therefore stipulated in the invitation for tenders for this project.
The pipe arch method is the safest and most efficient way of constructing tunnels of large diameters over short distances. In Moscow a Herrenknecht microtunnelling machine drove the steel pipes forward. The jacking frame - fixed to a horizontally and vertically adjustable platform - enabled 50 borings to be made for the pipe arch. The desired cross section, (29 meters wide and nine meters high), was then excavated. Incidentally, rail traffic also ran without a hitch during construction.