Construction of the San Francisco Bay Tunnel

摘要

The Hetch Hetchy water system, owned and operated by the San Francisco Public UtilitiesrnCommission (SFPUC), serves 2.4 million people within the greater Bay Area. The system crosses under thernSan Francisco Bay and required replacement of 1920s-era seismically vulnerable pipelines with a tunneledrnsection.rnThe Bay Tunnel was the first TBM-driven tunnel underneath the San Francisco Bay. It was constructedrnusing an Earth Pressure Balance machine with specific ground conditioning capabilities. The tunnel is approximatelyrneight kilometers (five miles) long with an excavated diameter of 4.6 meters (15 feet). The projectrnencountered ground that varied from extremely hard, stiff clays with interbedded sands and silts, to a section ofrnhard rock near the end of the tunnel drive.rnThis paper focuses on the construction means and methods used to facilitate the typical progress ofrnapproximately 38m (125 feet) per day over two ten-hour shifts.