Tunnel behavior detected through displacement measurements is valuable information to refine the design of the support and the lining, in a reliable way. To take advantage of the data thus obtained, an analytical method to reproduce the measured behavior is required. To date, the only available such a method is the result of applying the Elasto-Plastic Theory to the particular case of a tunnel driven through a subsoil mass where the original vertical and horizontal pressures have the same value : Ko = 1, (Deere et al. 1969). However, in general those two original pressures are not equal and therefore, proper use of the measured behavior of the tunnel calls for an extension of the Elasto-Plastic Theory to cover the cases where Ko ? 1; the fundamental assumptions and results for and from that extension of the Theory are described in this paper.
To reproduce in an analytical and general way the deformational behavior of a tunnel driven in a subsoil mass in which the original vertical pressure, Pv, is not equal to the original horizontal pressure, Ph, it is required to extend the Elasto-Plastic Theory available forthe case Ph = Pv ,that is Ko = 1, (Deere et al. 1969), to cover the cases where Ph ? Pv, Ko ? 1, anticipating that the plastic limits in the horizontal and vertical directions will have different radial distances from the center of the tunnel and, moreover, that a plastic zone could develop only in one of those directions.