Examination of the use of continuum versus discontinuum models for design and performance assessment for the Yucca Mountain site
This report examines the use of continuum and discontinuum numerical methods for analysis of the thermomechanical response of the rock mass at Yucca Mountain. Continuum numerical methods consider the rock to be a solid, unfractured body, whereas the discontinuum method is formulated specifically to account for the effects of discrete fractures. The fractures within the rock introduce overall non-linear material response due to slip and separation of rock blocks. Continuum models attempt to simulate this response through the use of non-linear constitutive laws. Discontinuum methods attempt to simulate the true response of the rock mass by correctly modeling the behavior of the joints as well as the deformability of the intact rock blocks. It is shown that, as the joint spacing, s, becomes small with respect to the size of the excavations, the behavior of the jointed rock approaches that of a solid with a form of elasto-plastic constitutive behavior. It is concluded that a continuum model with a form of ``ubiquitous`` or ``compliant joint`` plasticity law is probably sufficient for analysis of the thermomechanical response of excavations in welded tuff. However, one of the questions concerning Yucca Mountain which remains is the effect of fault structures on the stability performance of the repository, particularly under thermal and dynamic loads. Here, a true discontinuum approach seems necessary. 45 refs., 42 figs., 4 tabs.
- Research Organization:
- Nuclear Regulatory Commission, Washington, DC (United States). Div. of High-Level Waste Management; Itasca Consulting Group, Inc., Minneapolis, MN (United States); Itasca Consulting Group, Inc., Minneapolis, MN (USA)
- OSTI ID:
- 137516
- Report Number(s):
- NUREG/CR-5426; ON: TI89016813; TRN: 89:024259
- Resource Relation:
- Other Information: PBD: Aug 1989
- Country of Publication:
- United States
- Language:
- English
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