Introduction to tunnel construction / Введение в строительство туннелей

Tunnels are unlike any other civil engineering structures. In buildings or bridges, the building materials have defined properties and they can be tested to ensure they meet these, whereas this is not the case in tunnelling. Table 1.1 illustrates some of the issues associated with tunnel design when compared to above ground construction projects. Although a tunnel structure often needs support systems made up of concrete and steel, it is the ground that is the major part of the structure, and this can have both a supporting and a loading role. The key to successful tunnel construction is therefore to understand this material, in particular its strength and stability characteristics. No matter how much of the ground we test in preliminary site investigations and how many borehole cores we take for testing in the laboratory, we can only ever test a small fraction of the total ground to be affected by the tunnel construction. Therefore, it is up to the engineer to determine the relevant ground conditions and its associated properties. However, since only a small fraction of the material can be tested and with limited knowledge of, for example, the effects of layering, fissures and discontinuities, much of this assessment is based on judgement and experience. One might even suggest that emotions are involved. So how can this then be used as the basis for tunnel design? It is up to engineering judgement to interpret the site investigation report and suggest suitable design and construction techniques. <...>