ABSTRACT
We consider a shallow cylindrical tunnel of diameter D crossing a dry, cohesionless soil obeying the Coulomb yield criterion with the friction angle φ. The depth of cover amounts to H (Figure 1). The tunnel wall is supported by a rigid lining up to a distance e behind the face (Figure 2). The force S that is needed in order to stabilize the face will be estimated by considering the limit equilibrium. The failure mechanism according to Horn (1961) approximates the circular face by means of a square and consists of a wedge and the overlying prismatic body (Figure 1). The side length b of the
1 INTRODUCTION
The collapse of the face of a shallow tunnel may propagate towards the surface, thereby creating a crater and leading to third party damage. In order to assess the risk and to design appropriate countermeasures, it is essential to have reliable analyses of face stability and predictions of the necessary support pressure. The stability of the tunnel face is usually analyzed by limit equilibrium calculations and occasionally by numerical models (cf., e.g., Vermeer et al. 2002; Kirsch 2009).
