Some Geotechnical Characteristics of the Subway Construction in Sofia City, Bulgaria

Sofia subway is already in operation for 18 years although its network expansion continues. At the bottom of its development lay the accumulated experiences from the cities like Moscow, St. Petersburg, Paris, Vienna, Berlin and others.Sofia is a city with more than 2000 years of history; with several archaeological layers and diverse geological and tectonic conditions. All these characteristics are a prerequisite for complex technical solutions and many challenges to the engineers when they meet unexpected surprises in the geological profiles or underground infrastructure.The report will present to your attention four situations where along the tunnels route there were unexpected faults or water from the water sewerage network appearing. The above is accomplished with description of the technological solutions to such situations and applied modern geophysical surveys for rapid diagnosis of failures.