ABSTRACT
The excavation of a shallow tunnel is clearly a threedimensional problem. Neglecting the effect due to the volume loss at the front face of excavation, this problem might be analyzed under plane conditions. Figure 1 shows an idealization of shield tunnelling, where a circular tunnel of diameter D is constructed with a depth of cover C. The tunnel lining is regarded
as rigid and in front of it the tunnel heading is represented by a cylindrical cavity of length P in which a uniform fluid pressure σt acts, and a uniform pressure σs acts on the soil surface (Figure 1a). For relatively big value of the distance from the tunnel lining to the tunnel face, the problem can be idealized under plane conditions (Figure 1b).
