Düzbağ Tunnel (Çağlayancerit-Kahramanmaraş) support systems design

During the portal excavations and mirror excavations in the tunnels, unwanted instabilities may be observed from time to time due to weak rock conditions, discontinuities and new stresses. In order to prevent these instabilities and for successful tunneling, the rock mass properties must be accurately demonstrated. Various methods have been developed based on empirical, analytical and measurement observations in determining rock mass properties. Rock mass classification systems have been finalized as a result of various changes as a result of applications and cover the most intensive usage area as a part of daily works in tunneling applications. In this study, the instabilities during the excavation of portal and tunnel mirrors due to weak rock conditions in flatbath tunnels in Düzbağ drinking water construction and support methods applied to prevent these instabilities were investigated. Tunnel excavation was carried out in full cross-section by using düzgün cutting and blasting technique. The inner diameter of the tunnel is 6.30 m. In the tunnel, shotcrete, rock bolt, steel shoring and wire mesh were used as supporting elements. In determining the geotechnical properties of rock mass, discontinuities in tunnels and portals and rock mass defeat criterion, Hoek Brown defect criterion, classification RMR, Q and NATM systems used in determination of rock mass properties, 3D deformation was performed in measurement of movements occurring in tunnel and portal excavations. The entire transmission tunnel; deposited in shallow-neritic facies; In the upper part, light cream colored, clayey, calcareous and sometimes cherty limestones, in the lower part, yellowish colored massive, dolomitic and sometimes chert nodular limestone stacked, and will be opened within the Midyat group. Due to its proximity to the Eastern Anatolian fault, it is extremely fractured and additive with crush zones.