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The Exploratory Studies Facility is currently under construction at Yucca Mountain, Nevada. The purpose of the Exploratory Studies Facility is to characterize rock strata for its suitability to construct a nuclear waste repository. At the current stage, a considerable amount of underground work has been performed providing direct access to the rock mass interior. This access facilitates verification of the initial estimates of the magnitudes of rock strata parameters and allows for evaluation of the ground support system(s) performance based on the field-acquired data. As mandated by federal law (10 CFR 60), the engineering design at the Yucca Mountain Site Characterization Project must be supported by evaluation of the performance of the underground openings based on field-acquired evidence. This paper presents a discussion of selected elements of the Performance Confirmation Program that were designed to provide verifiable evidence of the in situ performance of the underground openings and ground support system through measurements performed in the field. The two aspects of the Performance Confirmation Program are presented, namely, the results of ground deformation monitoring and the results from strain gage measurements of steel set loads. The deformation monitoring analysis presents a semi-empirical approach for analyzing the initial, unmeasured portion of the tunnel deformation, and for predicting future opening displacements. The steel set loads analysis presents the development of a numerical model that provides the ability to examine various steel set support concepts and to optimize the performance of the steel set given the operational constraints in the field. |
