Evaluation of deformation field between km:31+500 – 31+530 in Samanlı-Orhangazi tunnel (Yalova-Bursa) by utilizing numerical models

In this study, the geological and geotechnical properties of rock units, located in project route of the Samanlı Tunnel constructed as a double tube between 30+830 and 34+244 kilometers of the Gebze – Orhangazi – İzmir Highway were investigated. As a result of the geological studies, it is determined that, Precambrien aged metamorphic rocks (metasandstone, metaquarsite, gneiss) and Eocene aged volcanic rocks (aglomera – basalt, andesite – dasite) were outcropped in the area. Studies to determine the engineering properties of the units that are found in the tunnel route is conducted. Geotechnical characteristics of the units were determined by using the laboratory experiments and empirical equations. During tunnel excavation, geotechnical units classified according to the RMR, NATM and GSI system, and the necessary support elements are determined for the tunnel. Total principal displacements (deformations) and stresses occured on support elements was determined using finite element method software Phase2 7.0. Deformations occured during tunnel excavation and support stages , was recorded by optical measurements. Deformations determined using numerical analysis were compared with the actual values of deformations. Specified supporting elements and adequacy of the support members was investigated. Geological studies in the excavation stages and correctly interpreted deformation measurements has been amended on support system in line with the philosophy of the NATM. As a result of the amendments, the cost of the tunnel, security and progress rate is positively affected. KEYWORDS: Tunnel, geotechnics, Samanli Tunnel, engineering geology, rock mass classification, finite element method, deformation analysis, New Australian Tunnelling Method (NATM)