Empirical and numerical analyses of support systems of Macka (Trabzon) tunnel

In this study, the engineering properties of the rock masses along the Macka Tunnel route and the optimum support systems will be used during excavation are aimed to determine. The reliability of the support systems obtained from empirical methods is evaluated by numerical analysis. The units at the study area are Early Turonien aged Çatak Formation, Turonien-Santonien aged Maçka Formation, Turonien-Santonien aged Esiroglu Formation and Early Campanien aged Kackar Rhyodacite. 236 m of the excavation will be carried out in Esiroglu Formation, 1410 m in Kackar Rhyodacite and 1125 m in Catak Formation. Studies were carried out three stages as field, laboratory and office studies. By the field studies, detailed geological map of the tunnel route was done, line surveys were carried out to determine the engineering properties of discontinuities. Drilling cores were examined thus Rock Quality Design (RQD), total core recovery (TCR) and weathering degree (W) of the rock masses were determined. Also, core samples were taken for laboratory studies. By the laboratory studies, mechanical, physical and elastic properties of the rock materials were defined. During the office studies, the rock masses along the tunnel route were classified by Rock Mass Rating (RMR89), Rock Mass Index (RMi), Rock Mass Quality (Q), Geological Strength Index (GSI) and New Australian Tunneling Method (NATM) with the data obtained from both field and laboratory studies. The applicability of the support systems suggested by RMR89, Q and RMi, thickness of the plastic zone and the effect of the displacements around the tunnel were analyzed numerically by using Finite Elements Method (FEM). Optimum support systems were defined considering the results of numerical analyses. According to the results of numerical analyses; for the crown of the tunnel, shotcrete thickness suggested by RMR89 classification system and the bolt spacing suggested by Q classification system are similar to one which is suggested in this study. For the walls; bolt spacing of Q classification system, bolt length of RMi classification system and shotcrete thickness of RMR89 classification system are similar to one which is suggested by this study. When the support systems suggested in this study are compared with support systems suggested by RMR, Q and RMi classification systems, it was determined that the support system suggested in this study were compatible with the support systems suggested by RMi classification system.