Within the scope of “Istanbul - Ankara High-Speed Railway Project”, “Design and Construction Works Between Geyve - Sapanca (Dogancay Ripaji)”, there are a total of 8 tunnels including 2 main tunnels and 6 security tunnels. The T2 tunnel with a total length of 4667 m with a diameter of 13 m and the security tunnels (GT-4, GT-5 and GT-6) of the T2 tunnel with a total length of 2049 m are being carried out by Soner Temel Mühendislik İnşaat ve Ticaret A.Ş. Within the scope of the specified tunnels, site mobilization was completed at five different points, and work began on February 19, 2020 with a term sheet dated February 17, 2020 and a subcontract dated March 2, 2020.