Effectiveness of pressure relief shafts – full scale assessment

The use of pressure relief shafts has often been proposed as a means of reducing pressure fluctuations and of improving passenger comfort on board high-speed trains in tunnels. The recently opened rail-link between Mattstetten-Rothrist in Switzerland is one of the first rail projects where such shafts became an integral part of the project right from the design stage. The effectiveness of pressure relief shafts has been proven during the commissioning phase of this 45 km long new rail-link. Several aerodynamic measurements were conducted in different tunnels with and without pressure relief shafts and with different train types. One example is the double-track Emmequerung tunnel with a free cross-sectional area of Atunnel = 76 m2 with two pressure relief shafts (Ashaft = 12.25 m2). The same tunnel without any pressure relief shafts would have required a larger free cross-sectional area of Atunnel = 105 m2 in order to satisfy the project specific comfort criteria for various train types (∆ptrain < 1.5 kPa within 4 s). In general, smaller tunnel cross-sections lead to reduced construction costs. Furthermore pressure relief shafts can be combined with additional functions (egress path, smoke extraction, climate improvement, etc.). These advantages must be balanced with possible disadvantages (noise emissions, increased local air flows in the tunnel, etc.) and the limitations (ground overburden). The experience gained from the new Swiss rail-link shows that under certain conditions pressure relief shafts are effective and reasonable. 1