Discussions About Tunnels Accidents Under Squeezing Rock Conditions and Seismic Behavior: Case Study on Bolu Tunnel, Turkey

Abstract

Tunnel Engineering has been modernizing to increase workplace safety and minimize the risk of collapse, mainly in the construction phase, which, statistically, has the highest number of accidents. This accidents on tunnels can be caused by different origins, depending on factors such as geology, natural disasters, poor planned or executed project and even lack of maintenance. However, in tunnel construction, two cases draw the attention of engineering due to the damage caused: effects of seismic behavior and squeezing rock. The impact of seismicity must be analyzed in a tunnel project, since it is an underground work, whose mass is directly susceptible to this action. Besides, the combination of unfavorable effects on the safety of the work with the effects of earthquakes must be verified. The impacts of squeezing should also be taken into account. Thus, rocks studies that present such behavior must be made for a better understanding of their behavior and critical deformations due to the loading imposed by the excavation. This paper discusses the lessons learned in tunnel constructions in regions where the squeezing rock phenomenon occurs and its complication in seismic zones. Therefore, a case study was carried out as a result of the accident in the Bolu tunnel, Turkey, whose results demonstrated the rupture of the twin tunnels due to an earthquake and the presence of squeezing rock.