The damage and response of some underground structures by the 2023 February 6 Great Turkish Earthquakes and some considerations

Two successive disastrous earthquakes occurred on February 6, 2023 in the province of Kahramanmaras, of T & uuml;rkiye. These earthquakes resulted in loss of more than 50.000 lives and several cases of serious damage to various engineering structures. Some roadways and railway and underpass tunnels were also damaged by the earthquakes as a result of heavy shaking as well as faulting. In addition, many rockfalls occurred at the portals of railway and roadway tunnels. The faulting caused quite severe damage at the railway tunnel near Ozan village. The concrete lining of the new Erkenek tunnels ruptured at several places. The damage in the new Erkenek twin tunnels may be related to mass movements caused by heavy ground shaking as well as an inclined geological structure together with low overburden next to a valley. Sinkholes of man-made and natural cavities occurred in several locations including urbanized areas. In this study, the authors describe the damage to underground structures by the doublet Kahramanmaras, earthquakes with some detailed analyses of Erkenek tunnels. Furthermore, the causes of the damages are described and their implications on the seismic design of underground structures are discussed. The observations indicated that underground openings crossing by faults and fracture zones may be enlarged to accommodate relative slips along faults and fracture zones. Furthermore, the ductility of support should be high in such zones in order to prevent brittle failure, which may have very disastrous effects. In addition to man-made underground structures, natural underground rock structures may be damaged or sinkholes may be caused by earthquakes as observed in the 2023 Kahramanmaras, earthquakes. The computational results clearly explain why the valley-side of one of the tunnels was more damaged compared to that of the mountain-side tunnel. It is also noted that some of the sinkholes in the earthquake region can be explained using some techniques available in literature.