264 black. PERMAFROST [Ch. 14 



Construction 



Two types of construction methods are used in permafrost areas 

 (Muller, 1945). In one, the passive method, the frozen-ground condi- 

 tions are left undisturbed or provided with additional insulation, so 

 that the heat from the structure will not cause any 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 pre- 

 liminary examination, of course, is necessary to determine which pro- 

 cedure is more practicable. 



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

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

 tion be used; in (b) or (c) either the passive or active method 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 are presented by Hardy and D'Appolonia (1946) ; Corps of 

 Engineers (1946, 1945) ; Muller (1945) ; Huttl (1948) ; and Zhukov 

 (1946). Refinements 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 largely in unpublished reports of various federal agencies.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 Pryor (1945) have shown that road icings are more com- 

 mon 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 the water 

 content. Methods of predicting by moisture diagrams the amount of 

 settling of buildings on thawing permafrost are presented by Fedosov 

 (1942). 



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 

 regime, to promote pergelation or depergelation as desired. Generally 

 the former is difficult near the southern margin of permafrost. If the 

 existing climate is not cold enough to insure that the permafrost re- 



