Summary: | In the CRREL tunnel (Fig. B1, B2), sublimation is extremely apparent, but because of the tunnels limited usage it poses no significant problems. However, in an operating mine with forced air ventilation and continuously operating machinery, the problems associated with sublimation may no longer be insignificant. The dust released by the evaporating ice poses not only the obvious respiratory threat, but an additional safety threat, as fine silt suspended in the air reduces visibility, and removal or suppression of the dust will be of importance. Sublimation control measures of the permafrost in the CRREL tunnel -- Introduction -- The sublimation process -- Sublimation control -- Test installations -- Conclusion -- References -- Appendix A: Summary of data -- Appendix B: Photographs.
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