Block Dynamics Modeling in Support of Seismic Designby L. J. Lorig, Itasca Consulting Group, Inc, Minneapolis, United States,
R. D. Hart, Itasca Consulting Group, Inc, Minneapolis, United States,
Abstract: The behavior of an underground excavation is usually characterized by stresses and displacements which develop around the excavation as a result of prevailing field conditions. For conventional pseudo-static design, these conditions include rock mass strength, deformability, initial in-situ stresses and groundwater pressure distribution. Conditions which are not routinely included but which, nonetheless, may need to be considered for a high-level nuclear waste repository, are thermal and seismic loading. Numerical methods which are used to study the behavior of underground excavations treat the rock mass as an equivalent continuum. However, experience and analysis suggest that shear displacement at joints may have an important effect on excavation performance. The distinct element code UDEC (Itasca, 1991) is presented in this paper as one numerical program to model discontinuum or block dynamics. Considerations in dynamic modeling of jointed rock are emphasized, and an example of the dynamic behavior of an excavation in a thermally-stressed medium is shown.
Subject Headings: Excavation | Rock masses | Dynamic models | Seismic design | Pressure distribution | Seismic loads | Underground structures | Thermal properties
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