Quantitative Analysis on the Minimum Support Load for Tunne lling

Abstract: ABSTRACT: This paper addresses the problem of assessing the stability conditions of shallow excavations. A closed-form statically admissible solution, which allows an estimation of the support pressure where the cavity is at the verge of equilibrium, is presented. The solution has been derived with the assumption that the circular opening is excavated in ground modelled with the Mohr-Coulomb material. Graphical representations on the relationship among parameters in the analytical expression, the depth of the tunnel opening in relation to its radius, and the effect of the support pressure in relation to the cohesion and the frictional angle of ground, are presented. A series of quantitative analysis using the finite element method is reported. The results of the simulation show that the analytical solution gives the minimum support pressure to keep the stability of the ground during excavation.