EARTH, SAND-CLAY, AND GEAVEL ROADS. 31 



keep the above force busy. With such a force the number of wagons 

 for maximum efficiency varies from about 3 for a 500-foot 

 haul up to about 12 for a haul of 1 mile. Ordinarily, one of the 

 plow teams may be employed in hauling for at least a part of the 

 time. 



Under average conditions such a force as that described above 

 should move about 150 cubic yards of earth per 10-hour day. 



BUILDING EMBANKMENTS. 



One of the most important considerations connected with the 

 grading of an earth road is the stability of the embankments. 

 Where a road is situated in a cut and is well drained, it is not likely 



,1 \\" . 



•:'■■■..: ' 





^sjk 



1 



! "7 





r "^. * - sytt^. 



V-''' ■"'" * A 



■ 



H58Sp&iL.>..:«M 







* -■C" M s*" SPSS 



_ „, OPRREI3I76 



Pig. 19. — Steam shovel at work. 



to be affected seriously by such agencies as shrinkage, settlement, and 

 slipping, any one of which may injure or destroy a road situated on 

 a poorly constructed embankment. In grading a road, therefore, 

 the methods employed in building the embankments are deserving 

 of much more careful scrutiny than those employed in making 

 excavations. 



To prevent a road over an embankment from being damaged by 

 shrinkage of the material forming the embankment, the material 

 must be free from vegetable matter and uniformly compacted as it 

 is deposited. Where the road surface is to be of earth, the embank- 

 ment usually may be compacted sufficiently to prevent injury from 

 shrinkage by spreading the material in relatively thin horizontal 

 layers and letting each layer be compacted by the grading teams as 

 the succeeding layer ; s being spread. Layers of ordinary earth, not 



