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  SEE Tunnel: Promoting Tunneling in SEE Region

  Swelling and squeezing rocks have different deformation mechanisms. However, significant deformations may occur in both rock types in tunnelling. Deciding the support system in swelling and squeezing rocks is one of the big challenging issues for rock engineers. Because there are many facts and problems has to be considered as/like the support type, the performance of the support, the support element, the rock parameters, the condition of the rock structure and creating an appropriate support strategy. Besides all these issues, parameters like excavation geometry, round length (distance from face to closed the support) and excavation rate affect the support performance directly. The TH type steel supports, which were used in deep underground mine headings at old times, are started to be used as “yield-control support system” in tunnels recently. However, sliding ability of the TH steel support allows cross-section contractions. If convergence amount can’t be calibrated, re-shaping studies have to be done at the excavated areas due to the occurrence of time-dependent creeps especially in swelling and squeezing rocks. This situation increases the project costs and causes an important waste of time. Also, numerical model studies for highly swellable and/or squeezable rocks must represent the time-dependent creep behavior of the rock. Analyses that made only with failure parameters are insufficient. Simple stiffness parameters like time-dependent creep, swelling index, compression index should be added to the model. Otherwise it just becomes a simple inadequate approach and leads rock engineers to make wrong decisions. It is possible to constitute a high performance support system in this type of rocks by choosing appropriate round interval, using a non-deformable and heavier I profile and using sufficient parameters obtained by analysis.

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