Unique engineering problems are encountered in the design, construction, and maintenance of facilities in permafrost areas. Changes to the thermal regime of permafrost produces corresponding changes in the mechanical and physical properties of the soils. Degradation of permafrost can result in large settlements which commonly are differential and hence more damaging or detrimental to the operation and performance of structures, utilities, roads, and airfields. The degradation of permafrost may be caused by building heat or from disturbance to the ground cover, solar radiation, drainage, underground utilities, groundwater flow, or by construction methods. An assessment of the potential settlement associated with the thawing of permafrost is therefore essential, and require a thorough understanding of frozen soil mechanics.

The known occurrence and distribution of ice in permafrost and the basic relations between volume and weights of frozen and thawed soils can be shown in diagrams and sections, and can be expressed by appropriate equations. Laboratory test results on thaw-consolidation

End_Page 2475------------------------------

of undisturbed frozen cores from several locations are of considerable interest. Although most frozen soils tested contained freshwater ice, some plastic silt and clay samples containing significant quantities of brine also were tested. The latter samples were obtained at Kotzebue and Point Barrow, Alaska.

The writer shows the identity between the consolidation theory advanced by Terzaghi for thawed soils, using void ratios, and the relation between frozen and thawed dry unit weight of soils. On the basis of this identity, one may estimate quantitatively the total settlement from information in single boreholes and the differential settlement between 2 or more adjacent borings. There also are methods for building in ice-rich permafrost areas, including methods of preserving the frozen state or pre-thawing and consolidating.

End_of_Article - Last_Page 2476------------