The U.S. Army Cold Regions Research and Engineering Laboratory (USA CRREL) permafrost tunnel near Fiarbanks, Alaska, was recently enlarged. A new winze and lower room were constructed in the tunnel, permitting examination of new silt exposures and previously unexposed, stratigraphically lower gravels and bedrock. From these exposures additional stratigraphic information was obtained by radiocarbon dating; new data on the material properties of the perennially frozen gravels were also acquired. (Author).

A mechanical method of tunneling in permafrost was investigated by excavating the Alaska Experimental Permafrost Tunnel in a perennially frozen stratum of Fairbanks silt at the edge of a gold dredge field 11 miles north of Fairbanks. The tunnel is 360 ft long and about 7 x 13 ft in cross section. It was cut by the Alkirk continuous cyclic mining method. Certain properties of the frozen silt were investigated and the tunnel was evaluated as a shelter for military purposes. Temperatures, mechanical compositions and moisture contents are discussed and observations on plastic deformation are given. The machine uses a pilot-pull principle to provide face pressure. Its potential performance was evaluated. Special observations of cutting strain and power consumption were performed and the cutting process was analyzed. It was found that the mechanical process is expedient and that with modifications the Alkirk principle promises to become a feasible method of excavating deep shelters in permafrost. Subsurface shelters in permafrost provide advantageous protection against high velocity shocks. The operations' efficiency is analyzed in the appendix.