Technical Review of the Lined Rock Cavern Concept and Design ...

Technical Review of the Lined Rock Cavern (LRC) Concept and Design Methodology 12
Figure 4-4 Sand Dilation Along Shear Zones in the Uplift Experiment [after Mandl,
1988, pp. 71-75]
local scale. Although at shallow depths (less than 500 m), Ko is generally greater than
1.0, it is not always so. In many regions of the world, including the U.S., normal faulting
stress regimes exist where Ko would be close to or less than 1.0 (e.g., Mueller et al.,
2000).
As verification of the effects implied by Mandl (1988), the computer code FLAC (Itasca,
2000) was used to evaluate the soil-anchor analogy with a numerical model. FLAC
simulates materials as a continuum, and the code has been specialized to analyze soil and
rock-mechanics problems. An axisymmetric FLAC model of a soil anchor was prepared,
as shown conceptually in Figure 4-5. The model was verified by first comparing it to
experimental results of soil anchor pullout, and subsequently used to evaluate effects of
lateral pressure on such pullout. The effects of different anchor depths were analyzed for
the soil conditions listed in Table 4-1. The soil was represented as a Mohr-Coulomb
material with frictional strength only. While the high bulk and shear moduli values listed
in Table 4-1 are more representative of a rock mass than a soil, these values have an insignificant
effect on the anchor-pullout results. The results of the analysis are shown in
Figure 4-6, along with published experimental results (Vesi , 1971). Note that the
FLAC model results in Figure 4-6 reflect the use of Ko = 1; the results fall well within the
experimental data and validate the FLAC soil-anchor model to some extent.