The geotechnical investigation of the Cankurtaran (Hopa-Artvin) tunnel alignment and surrounding area

In this study, the geotechnical properties of rock units, located around and in project route of the Cankurtaran (Hopa-Artvin) Tunnel, planned to be constructed as a double tube between 7+980-13+208 kilometers of the Hopa-Borçka highway, were investigated. As a result of the geological studies, it is determined that, Late Cretaceous, Paleocene and Eocene aged sedimentary and volcanic rocks were outcropped in the area. The rock units, located along the project route, were grouped into the six geotechnical units and their enginnering properties were determined. The physico-mechanical properties of the intact rocks in each geotechnical units were found by performing the laboratory studies and the rock mass properties were determined by using the emprical equations. The geotechnical units were classified according to the RMR, Q, RMi, NATM and GSI classification systems by using data obtained from physico-mechanical properties, drilling studies and scan-line surveys and thus preliminary support design of the tunnel was designated. Using the finite elements method, support-rock interactions and deformations on the emprical support elements were determined. Stability of the tunnel portal and road cut slopes, planned to be excavated in the entrance and exit sections of the tunnel, were investigated by kinematical, limit equilibirium and numerical analyses and thus preliminary support elements were suggested for the unstable entrance portal slope. It was determined that, the allowable bearing capacity values of the geotechnical units, on which Subaşı Viaduct and Bridge No. 7 planned to be built, varies between qa: 8.37-11.20 MPa. The excavatability properties of the geotechnical units were defined by using the excavatability classification systems and it is determined that they are in ?digging? and ?ripping? classes.