PERMAFROST — BLACK 289 



temperature-measuring and recording devices are employed. Augers 

 and other mechanical means of getting at the permafrost are used 

 (Muller, 1945, and others). 



Construction. — Two types of construction methods are used in 

 permafrost areas (Muller, 1945). In one, the passive method, the 

 frozen-ground conditions are undisturbed or provided with additional 

 insulation, so that the heat from the structure will not cause thawing 

 of the underlying ground and weaken its stability. In the other 

 method, the active method, the frozen ground is thawed prior to 

 construction, and steps are taken to keep it thawed or to remove it and 

 to use materials not subject to heaving and settling as a result of frost 

 action. A preliminary examination, of course, is necessary to deter- 

 mine which procedure is more practicable or feasible. 



Permafrost can be used as a construction material (if stress or load 

 does not exceed plastic or elastic limit) , removed before construction, 

 or controlled outside the actual construction area. Muller (1945) has 

 shown that it is best to distinguish {a) continuous areas of permafrost 

 from (&) discontinuous areas and from (c) sporadic bodies. Russian 

 engineers recommend that in {a) only the passive method of construc- 

 tion be used; in {h) or {c) either the passive or active method can be 

 used, depending on thickness and temperature of the permafrost. De- 

 tailed information and references on the construction of buildings, 

 roads, bridges, runways, reservoirs, airfields, and other engineering 

 projects (pis. 9, 10, 11, and 12) are presented by Huttl (1948) ; 

 Hardy and D'Appolonia (1946); Corps of Engineers (1946, 1945); 

 Zhukov (1946) ; Muller (1945) ; Richardson (1944) ; and others. Re- 

 finements of the techniques and data on Alaskan research projects 

 (Wilson, 1948; Jaillite, 1947; Barnes, 1946) are contained largely in 

 unpublished reports of various federal agencies. 



Eager and Pry or (1945) have shown that road icings (pi. 10, fig. 3) 

 are more common in areas of permafrost than elsewhere. They, 

 Tchekotillo (1946), and Taber (1943b) discuss the phenomena of 

 icings, classify them, and describe various methods used to prevent 

 or alleviate icing. 



One of the major factors to consider in permafrost is its water 

 content. Methods of predicting by moisture diagrams (epures) the 

 amount of settling of buildings on thawing permafrost are presented 

 by Fedosov (1942). Anderson (1942) describes soil moisture condi- 

 tions and methods of measuring the temperature at which soil mois- 

 ture freezes. 



Emphasis should be placed again on the fact that permafrost is 

 a temperature phenomenon that occurs naturally in the earth. If man 

 disturbs the thermal regime knowingly or unknowingly, he must suffer 

 the consequences. Every effort should be made to control the thermal 



