FINITE ELEMENT CALCULATIONS OF THE MIGHTY NORTH EVENT Page: 3 of 10
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provide a significant opportunity to contribute to the understanding of the response of a lined tunnel in a jointed
brittle rock medium.
MIGHTY NORTH EXPERIMENT
The MIGHTY NORTH experiment (Figure 1) consisted of milled limestone bars, stacked around an aluminum-lined
"tunnel." A concrete test bed surrounded the test article. The test article was exercised with an explosively-driven
cylindrical shock wave. In addition to active data, precision measurements of individual "brick" dimensions were
made both during construction of the test article and during post-test decomposition.
AV1 AV2 AV3 AV4 AV5
Dilute Explosive 3.84 Iremite 42
Tiles (DET) with with Running
Detonation x2.74 m
Cylindrical 3.20 m
8.53 m Jointed 2.13 m
Test Article 406-mm-
Concrete Test Bed
1V FP1 FP2AV
AH6 - AH7
Iva, as6 JS2 LJs JS5 AAV1'
SA8 JS4 JS3 H1
A8 FP6 FPS 1
FPS F4 FP3 FP
4V12 . AV1 AV14
AH12 - H 11
0 Stress (FP)
Figure 1. MIGHTY NORTH test bed and test article detail .
Analysis of active gage data verified uniform response throughout the central portion of the test article along the
tunnel axis, confirming two-dimensional response in that section [2, 5]. The data also verified symmetrical response
about the vertical plane running along the tunnel axis. Additionally, the measurements and inspection of individual
bricks indicated that no plastic deformation occurred in the rock. On the contrary, deformation was fully attributed
to development of vertical rock fractures in individual bricks, forming an apparent "chimney," combined with liner
deformation and accompanying slip along the chimney fractures . Figure 2 displays the qualitative description of
the brick failures, showing the chimney formed above and below the tunnel. (Vertical displacements were
exaggerated by a factor of two for this plot .)
. Commnuton Fracture
Figure 2. MIGHTY NORTH jointed limestone
deformation and damage .
F1 n r -,iii
0 1 2 3 4 5 6 7
8 9 10
Figure 3. MIGHTY NORTH liner deformation
modal amplitudes .
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Steedman, D. & Swift, R. FINITE ELEMENT CALCULATIONS OF THE MIGHTY NORTH EVENT, article, December 1, 2000; New Mexico. (digital.library.unt.edu/ark:/67531/metadc723225/m1/3/: accessed February 23, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.