Design aspects of the alpha repository: IV. Structural analysis of excavation geometries. Technical memorandum report RSI-0030

The primary objective of the work effort presented in this report was to provide preliminary estimates of various facets of the structural stability of typical room-and-pillar geometries in the three candidate horizons of the proposed New Mexico site of the Alpha repository. In addition to the determination of the structural integrity of the excavation, a supplementary objective of the work effort was to analyze the macroscopic behavior experienced by the room and pillar geometries with the introduction of a large number of holes drilled in the room floor for the emplacement of canisters containing radioactive waste, along with the local structural behavior of the drill holes. Specifically, the analyses of these aforementioned configurations consisted of elastic finite element modeling of two different room-and-pillar geometries in each of the three candidate horizons. Each of those six models inherently contained the macroscopic ''stiffness'' of the proposed drill hole pattern in an effort to determine global pillar behavior. In addition to the room and pillar modeling effort, finite element models of the drill hole patterns were developed for each of the two room sizes and subsequently analyzed in each of the candidate horizons. These drill hole models assumed an ''in-line'' hole pattern. However,more » the ''off-set'' hole pattern was also analyzed and is presented in this report. In conjunction with the finite element analysis of the particular geometrical configurations discussed above, an analysis of roof behavior and rock bolting requirements was undertaken and is also presented.« less