Investigation of engineering problems encountered in tunnel structures using geophysical methods: The case of Doğanci Tunnel in Bursa province

Many engineering problems are encountered in the design of tunnel structures all over the world due to variable geological conditions. The purpose of this study is to examine the contributions of three different geophysical measurement methods in determining the possible water inflow and deformations from the side walls and ceiling of the Doğancı Tunnel in the Doğancı village of Osmangazi district of Bursa Province and to present solution suggestions. In this context, Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Multi-Channel Surface Wave Analysis (MASW) were taken on the right and left side walls of the tunnel, only GPR on the ceiling, ERT measurements were taken on the outer upper elevation of the tunnel and on the berm at the tunnel exit. According to ERT sections inside and outside the tunnel, resistivity values were obtained between 4-100 Ohm.m and 30-1000 Ohm.m, respectively, and according to MASW, S-wave velocity values were obtained between 150-600 m/sec. When all sectionswere examined, it was evaluated that the tunnel sections, where the resistivity and S-wave velocity were generally low and the GPR amplitudes were relatively high, mostly corresponded to significant deformations related to water inflow. These results show the importance of designing tunnel construction and subsequent reinforcement works according to geophysical measurements in terms of cost and safety.