Ground support for emplacement drifts at Yucca Mountain

Nolting, R.M., Duan, F., Sun, Y. Ground support for emplacement drifts at Yucca Mountain. 1998 Tunnelling Association of Canada
Annual Publication.
Ground support for emplacement drifts at Yucca Mountain
R. M. Nolting
Morrison Knudsen Corporation, Las Vegas, NV
F. Duan
Morrison Knudsen Corporation, Las Vegas, NV
Y.Sun
Morrison Knudsen Corporation, Las Vegas, NV
Abstract:
The stability of underground openings is being evaluated for a potential high-level radioactive
waste repository at Yucca Mountain, 170 km northwest of Las Vegas, Nevada. The repository
lies some 200 to 400 m deep in volcanic tuff above the regional groundwater level. Emplacement
drifts, emplaced with nuclear waste packages, will experience high radiation and wall rock
temperatures that approach 200°C for more than 100 years. These requirements have led to
consideration of full-circle concrete linings for support; however, modeling with ambient
properties shows that combined heating, excavation, and earthquake loads produce lining stresses
that are too high. Acceptable stress levels result with the modeling of temperature-dependent
properties, stress-reduction effects, and jointed precast concrete linings.
Resume:
La stabilite des ouvertures souterraines est couranment mesuree pour un depot de dechets
nucleaires it Yucca Mountain,situe it 170 km au nord-ouest de Las Vegas dans le Nevada. Ce
depot se trouve it 200 ou 400 m d'epaisseur dans la roche volcanique, au-desus du niveau de la
nappe phreatique regionale. Les galleries d'emplacement, ou seraient places les emballages de
dechets nucleaires, subirront un haut niveau de radiation, ainsi que le mur du rocher avec des
tempertures approchant les 200°C pendant plus de 100 ans. Ces criteres ont necessite le soutier
par le betonnage de la paroi du tunnel, mais le modele des proprietes ambiantes demontre que la
chaleur, le creusage et le tremblement de terre produisent des charges tres hautes sur la paroi. Les
charges acceptables sont achevees grace it l'usage de la temperature ambiante en ajoutant l'effet
de la relaxation des contraintes et en utilisant le beton precoule segmente.
Keywords: volcanic welded tuff; thermal and mechanical rock behavior; Thermally-induced
stress and deformation; Cooling and Heating Cycles; Ground support design; Options for LongTerm Rock Support; Lining Stress and Strain; ESF tunnelling.
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