Observations on the influence of lithophysae on elastic (Young's) modulus and uniaxial compressive strength of Topopah Spring Tuff at Yucca Mountain, Nevada, USA

摘要

The mechanical properties of the Topopah Spring Tuff units at Yucca Mountain in the Nevada Test Site where portions of the United State's high-level nuclear waste repository tunnels will be located have been widely investigated since the early 1980s. Some of the units, most notably the lithophysae-rich units, have been the focus of research. The results of these studies demonstrated that the presence of lithophysae causes significant variability in elastic (Young's) modulus and uniaxial (unconfined) compressive strength of tuff. The Topopah Spring Tuff was created by the welding and subsequent cooling of pyroclastic flow deposits [1]. The thickness of the repository host horizon across the repository footprint is estimated between 195 and 220 m [2]. The repository is planned to be located in the middle to lower portion of the Topopah Spring Tuff unit. This section is densely welded with variable fracture density and lithophysae (or lithophysal cavities) [3].