652 whitmore. MILITARY GEOLOGY [Ch. 34 



order that such materials may be used wherever available, the follow- 

 ing laboratory determinations should be made for soil from the air- 

 field site: granulometric composition, specific gravity, moisture con- 

 tent, filtration coefficient, plasticity (for clayey soils), and coefficient 

 of internal friction (Bogomolov, 1945). 



Roads 



The military geologist, like the military engineer, is more concerned 

 with road maintenance than with construction. This is mainly a mat- 

 ter of locating ballast, fill, and surfacing materials; the geologic prob- 

 lems encountered are generally the same as those met in airfield con- 

 struction. 



Underground Installations 



Underground field fortifications have concerned geologists since 

 World War I (Brooks, 1920). During World War II, as a protective 

 measure against heavy bombing, the Germans went far in the con- 

 struction of underground factories. 



The term "hasty fortifications" will serve to include earthworks and 

 excavated defense works constructed or dug in the combat zone, as 

 opposed to permanent fortifications such as the Maginot Line. A hasty 

 fortification may be a slit trench, or it may be a complicated and ex- 

 tensive system such as that dug by the Japanese in the loess and marl 

 cliffs back of Kujukurihama, one of the beaches selected by the Allies 

 for the landings leading to the attack on Tokyo. Such works are al- 

 most always constructed in unconsolidated sediments. 



In such hasty construction, ground water presents a difficult problem. 

 To insure dry excavations by proper location and by effective con- 

 struction measures, it is of course highly desirable that the geologist 

 have logs of local wells. If these are lacking, air or ground reconnais- 

 sance and intensive study of large-scale soil and geologic maps or 

 aerial photographs will contribute much to the solution of the problem. 

 Seasonal fluctuations of ground water must be considered, together 

 with the water-bearing characteristics of various sediments. For in- 

 stance, von Bulow (1938) states that seepage water is concentrated in 

 the boundary zone between weathered and unweathered clay, usually 

 at a depth of 1 to 2 meters. 



Most extensive emergency military excavations are in lowlands; 

 therefore they must go below the water table. They must be pro- 

 tected by impervious strata to a thickness of at least 6 feet, or else 

 sealed off from ground water. Various means of effecting this are 

 discussed and illustrated by Brooks (1920). 



