Tallinn-Helsingi tunneli läbindamise puur-lõhketööde parameetrite väljatöötamine sinisavis ja graniidis [Bakalaureusetöö. Juhendaja: T. Tomberg]

The Tallinn-Helsinki tunnel would be the fastest railway connection between Estonian and Finnish capitals. The tunnel has a total length of 103 km. Inclined part of the tunnel from Estonian side from earth surface to the crystalline rocks is about 19,3 km. In the Estonian side the tunnel will start from the port of Muuga in Viimsi peninsula. The slope of the route is 1% to ensure the safety of fast-moving trains. The tunnel has a maximum depth of 180 m below the
sea level. Maximum rock pressure at the lowest point is 5,9 MPa. In total, two railway tunnels and one maintenance tunnel will be built, crossings will be developed after every 250 m and the channels for reducing the air pressure will be developed after every 200 m.

Mining conditions on the Estonian side of the tunnel are complicated due to artesian water and high rock pressure. To reach the crystalline basement, layers of sedimentary rocks must be passed through which the tunneling of each layer is different due to the variability of the mining conditions. Drilling and blasting method was selected as a tunneling technology. Tunneling starts with three parallel tunnels at the same time by drilling and blasting. The tunneling technology
and rock pressure were taken into account for choosing the tunnels configurations to find the optimal shape which guides the rock pressure away from the tunnel.

In this work, the parameters for drilling and blasting was elaborated in blue clay and granite. With each drilling and blasting cycle the frontline moves 2,5 m in blue clay and in granite it’s 3,4 m. After each blasting, the excavation site must be ventilated and supported with concrete.