Preliminary Assessment of Tunnel Stability for a Radioactive Waste Repository in Boom Clay

Abstract

This paper investigates the stability of tunnel galleries of a radioactive waste repository in Boom Clay, with specific reference to the current Dutch disposal concept. In this preliminary study an isotropic analytical solution has been implemented within a reliability based framework to assess the mechanical response of the Boom Clay, accounting for the aleatory uncertainty in soil property values. The performance, that is, the extent of the plastic zone with respect to a set limit state, is then quantified in terms of exceedance probability rather than using a single deterministic value. This allows for input into a quantifiable and more transparent decision making process. The effect of defining material parameter correlation within the statistical description of soil property values is illustrated via correlated and uncorrelated analyses. The results of this preliminary analytical investigation present a vital input for later two- and three-dimensional numerical modelling of the current disposal concept for a generic Dutch radioactive waste repository in Boom Clay, for both the pre- and post-closure analyses.