DRIFT GROUND SUPPORT DESIGN GUIDE Page: 35 of 190

                                
particular design are evaluated against the established structural acceptance criteria, and other
requirements, and the design determined to be either acceptable or to require modification.
"    Constructibility - The candidate designs, in addition to being evaluated for thermal-
mechanical and seismic stability, are evaluated on the basis of the results of constructibility
analyses, including the evaluation of the effects of construction and operational loads. As in
the previous bullet, results computed for construction and operational loads are compared with
the established structural acceptance criteria and the design determined to be either acceptable
or to require modification.
*    C9_ - Although not explicitly considered in this design guide, cost will be a consideration for
ground support systems that meet all other requirements.
The design methodology in practice extends beyond the identification of acceptable ground support
designs. Depending on the level of design, an additional step will be the production of certain
documentation. For example, if design is in a final stage, there will be detailed structural design,
contract documentation, including drawings, specifications, and procedures.
Another aspect of the methodology is implementation. This requires the collection and interpretation
of data from laboratory and in situ testing that meet Quality Assurance requirements and that cover
the appropriate range of repository conditions, considering the variability in geology and uncertainty
in measurement. Results of current testing in the ESF, including a drift-scale thermal test, alcove
tests, and possible testing through the full thickness of the TSw2 units; and future tests for material
properties are expected to provide a more complete database.
5.2 GROUND SUPPORT TYPES
Several types of ground support systems, suitable for both initial and final ground support are to be
evaluated for use in the repository area. Initial ground support will be required as a first pass (or first
stage) to stabilize the ground, especially where cast-in-place concrete linings are selected for later
installation. This situation will occur in emplacement drifts where it is required to do geologic
mapping, and a single pass lining, for example precast concrete, would make observation of the rock
surface difficult. In the case of precast concrete, final support would be installed essentially in one
stage, and thus would also act as initial support. Final support in the case of cast-in-place concrete
and some steel set systems is a separate step that follows the installation of the initial support.
Although the design guide addresses specific lining systems as candidates for final support of
emplacement drifts, these types are options whose final selection for license application design will
depend on the results of extensive analysis and testing that show the system meets all structural,
materials, operational, construction and waste isolation criteria. In particular, constructibility must
be given careful consideration, including such matters as the probable frequency of rock falls during
excavation, and the potential for debris to be carried above the shield and trapped behind the lining
during installation.

BCAA00000-01717-2500-00001 REV 00

September 1997

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