Analysis of emplacement borehole rock and liner behavior for a repository at Yucca Mountain

This report presents the results of studies aimed at assessing the quasi-static behavior of both the rock surrounding an emplacement borehole and the lining within an emplacement borehole for a nuclear waste repository in tuff. Two-dimensional thermomechanical analyses of conditions similar to those representative of the horizontal emplacement option were performed using a distinct element code. Three different behavior models (equivalent continuum, wedge, and parallel joint) were used to investigate the state of deformation at 0 and 100 years following waste emplacement. Three different rock strength assumptions were studied corresponding to ``design,`` ``recommended`` and ``limit`` values given in the Nevada Nuclear Waste Storage Investigation (NNWSI) Project Site Characterization Plan Conceptual Design Report (MacDougall et al., 1987). The ground reaction curve concept is introduced to study the potential liner loading resulting from thermally induced borehole closure. The report concludes that for the conditions and parameters assumed, liners may not be significantly loaded by borehole closure, because predicted closures will likely be less than tolerances required to install the lining. The report also concludes that gravity loading of linings by blocks which fall from the surrounding rock should not over-stress the lining. 25 refs., 51 figs., 14 tabs