ABSTRACT
This paper concerns of the measures taken to pass the gasoline contaminated area in Bakirkoy –Kirazli Metro Line, Istanbul. The project consists of two lines having a length of 8165 m each and two EPB-TBMs. During side investigations, it was discovered that an area close to the tunnel portal was contaminated by gasoline leakage coming from a petrol station, which is situated nearby to tunnels. According to the gas station authorities, fuel oil contamination was also found under another gas station approximately 60m North East of the present gas station. Within 100 m radius of the working area, there are residential apartments, parks, 4 schools and a big shopping mall. For that reason, to keep the hydrocarbon threshold below the exposure and explosion limits, several measures were taken. First, the pressure chamber was filled with bentonite in order to dilute the concentration of the hydrocarbons within the chamber. After a while, this application was abandoned since it caused the clogging of the cutterhead which effected the performance of TBM. As a second step, a gas monitoring system was designed and several gas sensors were installed at critical points of the cutterhead. In case of the gas increases in the environment, reaching to a predetermined level, the air velocity forced to increase in order to dilute the gas content. It is believed that the experience gained will serve a basis to overcome similar problems.
